23. 04. 2019 at 14:00S2 11/10 | ## SFB ColloquiumEvan O'Connor (Stockholm University) Core-Collapse supernovae are triggered by the implosion and subsequent explosion of the iron core in an evolved massive star. Since the core is shrouded from us by the overlying layers of the star, numerical simulations (and the odd neutrino detection of a Galactic supernova) are our best look into this extreme engine that powers one of the most energetic events in the Universe. Nature is 3D, and it is critical to simulate core-collapse supernovae in three dimensions because of the important hydrodynamic instabilities that can be present, however they are computationally expensive. With 1D and 2D models, we are now able to perform parameterized and systematic studies across a range of stars. Furthermore, in spherical symmetry we are able to achieve excellent agreement between otherwise completely independent codes. In this talk I will present a global comparison in 1D between six core collapse codes, an exploration of parameterized 1D explosions with over 1000 simulations and the beginnings of a systematic study of core collapse in 2D and simulations where we explore fundamentally 3D phenomena. I'll also present new results on the equation of state dependence of black hole formation. |

02. 05. 2019 at 14:00S2 11/10 | ## Theorie-SeminarLaura Moschini (Johannes Gutenberg-Universitaet Mainz) The breakup of 11Be, the archetypal one-neutron halo nucleus, is a particularly interesting case because, due to its short lifetime, it is one of the only ways to infer information about its structure. In that reaction, the halo neutron dissociates from the core during the collision with a target. When performed on a heavy target, like lead, the reaction is dominated by the E1 transition from the ground state. This transition is characterized by the dB(E1)/dE. This strength has been inferred from two experiments, one performed at 520AMeV at GSI [1] and the other at about 70AMeV at RIKEN [2]. Strangely the analyses of both experiments provide different E1 strengths. In this work we reanalyze them using the eikonal approximation to elucidate this discrepancy. To analyze the RIKEN data we adopt the dynamical eikonal approximation (DEA), which works well at intermediate energies; while for the GSI experiment we have developed a model for the high-energy collision properly taking into account relativistic effects, on both kinematics and dynamical aspects [3,4]. Our eikonal model includes a consistent treatment of both nuclear and Coulomb interactions at all orders. The description of the 11Be structure is provided by Halo-EFT [5,6] fitting the low- energy constants of this description onto structure observables, like the ANC of the bound states and phaseshifts in the continuum, predicted by an ab initio calculation [7]. Our cross sections for the 11Be breakup are in excellent agreement with both RIKEN and GSI data [6,8]. The dB(E1)/dE extracted from our structure model is in agreement with the RIKEN result, as well as the ab initio prediction [7]. We can conclude that the discrepancy between GSI and RIKEN E1 strengths arises from the method applied to extract this quantity from the experimental data. This new way of analyzing nuclear reactions performed to study the structure of nuclei away from stability has been extended to the case of 15C, another one-neutron halo nucleus, whose breakup has been measured at GSI and RIKEN at 605 and 68AMeV respectively [9,10]. In both cases, our reaction models have led to excellent agreement with the data [11]. |

09. 05. 2019 at 14:00S2 11/10 | ## Theorie-SeminarJohannes Weber (MSU) TBA |

23. 05. 2019 at 14:00S2 11/10 | ## SFB ColloquiumAnn-Cecilie Larsen (University of Oslo) TBA |

06. 06. 2019 at 14:00S2 11/10 | ## Theorie-SeminarJohann Haidenbauer (Juelich) TBA |

13. 06. 2019 at 14:00S2 11/10 | ## Theorie-SeminarClaudia Travaglio (INAF-Astrophysical Observatory Turin) TBA |

27. 06. 2019 at 14:00S2 11/10 | ## SFB ColloquiumAtsushi Tamii (Osaka University) TBA |

04. 07. 2019 at 14:00S2 11/10 | ## Theorie-SeminarDominik Schwarz (Univ. Bielefeld) TBA |

03. 04. 2019 at 14:00S2 11/10 | ## Theorie-SeminarMatteo Bugli (Department of Astrophysics (DAp), CEA Saclay) The characteristics of the initial magnetic field present in a supernova progenitor prior to collapse and the dynamics of the field amplification due to different dynamo mechanisms (such as MRI, convective motions, etc.) are to this date quite uncertain. |

07. 02. 2019 at 14:00S103/221 | ## SFB ColloquiumMichael Wiescher (University of Notre Dame) Primordial Stars are first generation stars that formed about 400 Million years after the Big Bang. Model simulations predict a mass distribution ranging from ten to several thousand solar masses. Their lifetime is short and a direct observation is unlikely. The observational evidence is in the abundance distribution of the subsequent second/third star generation, which is characterized by large carbon, oxygen abundances, with some more spurious heavier contaminants. This talk will present the various nucleosynthesis patterns possible in a primordial star environment and will discuss present experimental efforts to obtain a better understanding of the associated nuclear reaction rates. Preliminary results have been used to perform first star nucleosynthesis simulations for identifying the main reaction path towards the early origin of carbon and oxygen in our universe. |

31. 01. 2019 at 14:00S2 11/10 | ## Theorie-SeminarKari Rummukainen (University of Helsinki) Violent processes in the early universe can produce gravitational waves, which may be observable in future gravitational wave detectors, for example, the European Space Agency LISA satellite constellation. The primordial gravitational waves are a signal of physics beyond the Standard Model. In this talk, I describe how first-order phase transitions can generate gravitational waves and what kind of imprint they leave on the gravitational wave spectrum. |

24. 01. 2019 at 14:00S2 11/10 | ## Theorie-SeminarFrancesca Cuteri (Goethe-Universtaet Frankfurt) Knowledge of the nature of the chiral phase transition of QCD with two flavors of massless quarks is of great importance for further progress in various directions of particle and heavy ion physics. The closeness of the light quark mass values realized in nature to the chiral limit, makes it very plausible that the thermal transition of physical QCD, both at zero and at nonzero baryon density, might be affected by remnants of the chiral universality class. |

10. 01. 2019 at 14:00S2 11/10 | ## SFB ColloquiumWolfram Weise (TU Muenchen) This seminar presents a survey of our current understanding of dense baryonic matter from the point of view of hadronic chiral field theories and non-perturbative extensions using functional renormalization group methods. Constraints from neutron star observations are briefly reviewed. The so-called 'hyperon puzzle' in neutron star matter is outlined and a possible solution of this puzzle is discussed on the basis of hyperon-nuclear two- and three-body forces derived from chiral SU(3) effective field theory. |

18. 12. 2018 at 16:00S2 11/207 | ## Theorie-SeminarCaroline Robin (University of Washington) Nuclear excitations with isospin transfer play a crucial role in our understanding of nuclear structure, particle physics and astrophysics. A precise description of such transition modes is needed to compute the rates of weak interaction processes such as single- or double-beta decay which can provide information on the nature of neutrinos and are needed for the modeling of the r-process nucleosynthesis. |

13. 12. 2018 at 14:00S2 11/10 | ## SFB ColloquiumDaniel Phillips (Ohio University) For almost a century physicists have devoted intense attention to teasing out the nature of the nuclear force. But there remains much that we do not know about the way neutrons and protons interact, and the way that they come together to form nuclei. In this talk, I will show how two tools, effective field theory and Bayesian probability theory, can provide quantitative assessments of the impact of the things that we don't know about nuclear physics on the observables that are measured in experiments. |

04. 12. 2018 at 14:00S2 11/207 | ## Theorie-SeminarArianna Carbone (ECT*) Advancing the study of infinite nuclear matter has important implications on many branches of nuclear science: from the bulk properties of exotic nuclei to the equation of state of neutron star matter. After we have extended the self-consistent Green's function (SCGF) theory to account for three-nucleon forces, it is now possible to make reliable predictions of nucleonic matter at both zero and finite temperatures and with full chiral interactions, a task that was not possible until some years ago. The talk will present the SCGF approach as a very convenient way to investigate microscopic and thermodynamical properties of nucleonic matter. We will see how the prediction of the liquid-gas phase transition critical temperature in symmetric matter appears to be in reasonable agreement with experimental outcomes. Furthermore, I will present first-principle tests of thermal approximations used in equations of state to study stellar processes, which questions the validity of such astrophysical simulations. |

29. 11. 2018 at 14:00S2 11/10 | ## Theorie-SeminarJuergen Berges (Universitaet Heidelberg) |

18. 10. 2018 at 14:00S2 11/10 | ## Theorie-SeminarNicole Vassh (University of Notre Dame) The observations of the GW170817 electromagnetic counterpart last year suggested lanthanides were produced in this neutron star merger event. Lanthanide production in heavy element nucleosynthesis is subject to large uncertainties from nuclear physics and astrophysics unknowns. Specifically, the rare-earth abundance peak, a feature of enhanced lanthanide production at A~164 seen in the solar r-process residuals, is not robustly produced in r-process calculations. The proposed dynamical mechanism of peak formation requires the presence of a nuclear physics feature in the rare-earth region which may be within reach of experiments performed at, for example, the CPT at CARIBU and the upcoming FRIB. To take full advantage of such measurements, we employ Markov Chain Monte Carlo to "reverse engineer" the nuclear masses capable of producing a peak compatible with the observed solar r-process abundances and compare directly with experimental mass data. Here I will present our latest results given a low entropy accretion disk wind scenario and demonstrate how the method may be used to the learn which astrophysical conditions are consistent with both observational and experimental data. Uncertainties in the astrophysical conditions also make it difficult to know if merger events are responsible for populating the heaviest observed nuclei, the actinides. Here I will discuss a potential direct signature of actinide production in merger environments which would confirm mergers capable of being a dominant source of r-process material in the galaxy. However, an r-process which reaches the actinides is also likely to host fission, which is largely experimentally uncharted for neutron-rich nuclei. The influence of fission on lanthanide abundances, and the potential for future experimental and theoretical efforts to refine our knowledge of fission in the r-process, will be discussed. The question of where nature primarily produces the heavy elements can only be answered through such collaborative efforts between experiment, theory, and observation. |

27. 08. 2018 at 14:00S2 11/10 | ## Informal Theory SeminarSota Yoshida (University of Tokyo) Shell-model calculations are now playing key roles to investigate a wide variety of properties of nuclei owing to the developments in realistic nuclear potentials from chiral EFT and ab initio methods like IMSRG to derive effective interactions for a valence space. Under these circumstances, it is an urgent task to assess the validity of shell model itself, i.e. which states should be described within a given model space. In this seminar, I will talk about how to quantify the uncertainties in shell-model calculations, what could be concluded from that, and possible applications. |

31. 07. 2018 at 14:00S2 11/207 | ## Theorie-SeminarIngo Tews (INT) Neutron stars are astrophysical objects of extremes. They contain the largest reservoirs of degenerate fermions, reaching the highest densities we can observe in the cosmos. In August 2017, the first neutron-star merger, GW170817, has been observed, which provided compelling evidence that these events are an important site for the production of neutron-rich heavy elements within the r-process. |

12. 07. 2018 at 14:00S2 11/10 | ## SFB ColloquiumZsolt Poldolyak (University of Surrey) Information gained on neutron-rich N~126 nuclei is essential for the understanding of nuclear structure in heavy nuclei. Studies around doubly magic systems allow direct tests of the purity of shell model wave functions. From a longer-term perspective, experiments in this region pave the way toward the proposed nuclear-astrophysical r-process waiting point nuclei along the N = 126 shell closure. |

27. 06. 2018 at 14:00S2 11/10 | ## Theorie-SeminarDean Lee (Michigan State University) I discuss several recent developments and ongoing work in nuclear lattice simulations. The topics include improved chiral interactions on the lattice, eigenvector continuation, superfluid pairing in neutron matter, and the pinhole algorithm for nuclear structure and thermodynamics. |

14. 06. 2018 at 14:00S2 11/10 | ## Theorie-SeminarUlrich Heinz (The Ohio State University) The "unreasonable effectiveness" of relativistic fluid dynamics in describing high energy heavy-ion and even proton-proton collisions will be demonstrated and discussed. Several recent ideas of optimizing relativistic fluid dynamics for the specific challenges posed by such collisions will be presented, and some thoughts will be offered why the framework works better than originally expected. I will also address the unresolved question where exactly hydrodynamics breaks down, and why. |

07. 06. 2018 at 14:00S2 11/10 | ## SFB ColloquiumBrian Metzger (Columbia University) On August 17 the LIGO/Virgo gravitational wave observatories detected the first binary neutron star merger event (GW170817), a discovery followed by the most ambitious electromagnetic (EM) follow-up campaign ever conducted. Within 2 seconds of the merger, a weak burst of gamma-rays was discovered by the Fermi and INTEGRAL satellites. Within 11 hours, a bright but rapidly-fading thermal optical counterpart was discovered in the galaxy NGC 4993 at a distance of only 130 Million light years. The properties of the optical transient match remarkably well predictions for "kilonova" emission powered by the radioactive decay of heavy nuclei synthesized in the expanding merger ejecta by rapid neutron capture nucleosynthesis (r-process). The rapid spectral evolution of the kilonova emission to near-infrared wavelengths demonstrates that a portion of the ejecta contains heavy lanthanide nuclei. Two weeks after the merger, rising non-thermal X-ray and radio emission were detected from the position of the optical transient, consistent with delayed synchrotron afterglow radiation from an initially off-axis relativistic jet (or a shock-heated "cocoon" produced as the ejecta interacts with the kilonova ejecta). I will describe efforts to create a unified scenario for the range of EM counterparts from GW170817 and their implications for the astrophysical origin of the r-process and the properties of neutron stars (particularly their uncertain radii and maximum mass, which are determined by the equation of state of dense nuclear matter). Time permitting, I will preview the upcoming era of multi-messenger astronomy, once Advanced LIGO/Virgo reach design sensitivity and a neutron star merger is detected every few weeks. |

29. 05. 2018 at 14:00S2 11/207 | ## SFB ColloquiumLuna Pellegri (Wits University/iThemba LABS) The Pygmy Dipole Resonance (PDR), the low energy part of the electric dipole response in nuclei, is particularly relevant to investigate the nuclear structure and for its connections with photodisintegration reaction rates in astrophysical scenarios. Studies on the PDR are currently almost exclusively focused on spherical nuclei. For deformed nuclei several theoretical and experimental works have been performed to investigate the response of the Giant Dipole Resonance (GDR) while there are only a few on the PDR. |

17. 05. 2018 at 14:00S2 11/10 | ## Theorie-SeminarJavier Redondo (Zaragoza and MPI Munich) If the dark matter is made of axions and the Peccei-Quinn symmetry is restored after inflation, the distribution of dark matter becomes highly inhomogeneous at scales below a few milli-parsec. In such scenario, a sizeable part of the dark matter becomes bounded gravitationally in tiny dark matter halos, called axion mini-clusters. We are studying the formation of axion mini clusters starting from the initial density distribution predicted by numerical simulations in the early Universe until shortly after matter-radiation equality. This allows to predict the abundance and properties of these halos and their phenomenological implications. In this talk we will review the phenomenology of this very exciting and predictive scenario, our first results and, time-permitting, an overview of the experimental approaches to detect axion dark matter in this scenario. |

03. 05. 2018 at 14:00S2 11/10 | ## Theorie-SeminarBenoit Cote (Konkoly Observatory, Hungary) Galactic chemical evolution (GCE) is a multidisciplinary topic that involves nuclear physics, stellar evolution, galaxy evolution, and cosmology. Observations, experiments, and theories need to work together in order to build a comprehensive understanding of how the chemical elements synthesized in astronomical events are spread inside and around galaxies and recycled into new generations of stars. In this talk, I will present our efforts to create permanent connections between the different fields of research involved in GCE, highlight the impact of nuclear physics uncertainties on GCE predictions, and describe the challenges of using chemical abundances to trace the formation and evolution of dwarf galaxies in the early universe. I will also discuss the implication of the first gravitational wave detection of a neutron star merger event (GW170817, Abbott et al. 2017) on the evolution of r-process elements in the Milky Way, and present some of the future challenges that need to be addressed in the quest of identifying the main r-process site in the universe. |

19. 04. 2018 at 15:15S2 11/10 | ## SFB ColloquiumFrancesco Cappuzzello (University of Catania) The physics case of neutrino-less double beta decay and its tremendous implications on particle physics, cosmology and fundamental physics will be briefly introduced. In particular, the crucial aspect of the nuclear matrix elements entering in the expression of the half-life of this process will be deepened. The novel idea of using heavy-ion induced reactions as useful tools for the determination of these matrix elements will be then presented. The strengths and the limits of the proposed methodology will be indicated. New data from MAGNEX facility at the INFN-LNS laboratory give first evidences of the possibility to get quantitative results from experiments. Finally, the NUMEN project of INFN and the proposed strategy to this research will be sketched also in the view of the emerging technologies proposed. |

22. 03. 2018 at 14:00S2 11/10 | ## Theorie-SeminarHilla De-Leon (University of Jerusalem) The main source of energy generated in the Sun is a set of exothermic reactions (named the pp chain) in which 4 protons are fused into 4He. The first and the slowest reaction of this set is the pp fusion, which is a two-nucleon weak reaction that fuses two protons into deuteron and determines the Sun's lifetime. However, due to its long lifetime it cannot be measured, so its rate, which is proportional to the matrix element squared of the weak interaction between initial and final nuclear states, has to be estimated from theory only. |

08. 02. 2018 at 15:15S2 11/10 | ## SFB ColloquiumKei Minamisono (NSCL) Nuclear spin, electromagnetic moments and charge radius of radioactive nuclei are determined using laser spectroscopy techniques at the BEam COoling and LAser spectroscopy (BECOLA) facility at the National Superconducting Cyclotron Laboratory located in Michigan State University. The radioactive isotopes are produced using projectile-fragmentation reactions followed by in-flight separation and gas stopping. The scheme complements the reach over isotopes of ISOL-type facilities, where many laser spectroscopy data has been obtained for selected elements. BECOLA is currently the only laser spectroscopy facility that can accept radioactive beams from the fragmentation facility, and opens up new opportunities to explore key rare isotopes that have been difficult for laser spectroscopy to access before. I will introduce the BECOLA facility, and discuss recent results for neutron-deficient nuclei at the neutron shell closures N = 20 around Ca and N = 28 around Ni isotopes. |

01. 02. 2018 at 14:00S2 11/10 | ## Theorie-SeminarPierre Athuis (Saclay) In the recent years, ab initio methods have known a resurgence of interest among the nuclear theory community. Recent investigations [Tichai et al., 2016] have shown that Many-Body Perturbation Theory (MBPT), when using Hamiltonians evolved through the Similarity Renormalization Group method, could provide results competing with more demanding techniques like Self-Consistent Green's Functions or Coupled-Cluster. |

25. 01. 2018 at 15:15S2 11/10 | ## SFB ColloquiumMichael Jentschel (Institut Laue-Langevin, Grenoble) The ILL operates one of the most intense neutron sources in the world. Although primarily used for neutron scattering there exist a long-standing history of gamma ray spectroscopy at the ILL. The availability of well collimated intense neutron beams and in-pile sample irradiation positions allowed to develop quite unique instruments and applications of gamma ray spectroscopy. The talk will start with giving an overview on the different aspects of neutron based gamma ray spectroscopy at the ILL. Amongst the operating gamma ray instruments the ultra-high-resolution gamma ray spectrometers GAMS play a particular role due to their outstanding energy resolution and dynamic range. The instruments are based on perfect crystal Laue diffraction of gamma rays produced by excited nuclei in the reactor and their operation requires one of the worlds best angle measurement devices. Accordingly the experiments contributed in the past to many different fields in physics: nuclear structure, metrology, photon matter interaction, crystallography and astrophysics. In a second part the talk will review some highlights from the past 20 years of operation of these instruments. |

11. 01. 2018 at 14:00S2 11/10 | ## Theorie-SeminarAstrid Eichhorn (Heidelberg) I will discuss the asymptotic-safety paradigm as a framework for model of quantum gravity and matter at and beyond the Planck scale. I will highlight indications for the theoretical viability of this scenario and discuss how in this setting, Planck-scale physics could lead to testable consequences at the electroweak scale. In particular, the asymptotic-safety paradigm could have a higher predictive power than the Standard Model, and thus the values of free parameters of the Standard Model, such as, e.g., the values of the Abelian gauge coupling, the Higgs mass, as well as the Yukawa couplings of the heavy quarks, could be fixed uniquely by demanding asymptotic safety at the Planck scale. |

14. 12. 2017 at 14:00S2 11/10 | ## SFB ColloquiumHans-Thomas Janka (MPI Garching) First three-dimensional, first-principle simulations of core-collapse supernovae have become possible in the recent past. They demonstrate the basic viability of the neutrino-driven mechanism for powering the explosions of the majority of supernova progenitors. Although a number of open questions remain to be settled, the explosion models are now sufficiently mature to strive for detailed comparisons against observations, for example considering well studied, nearby supernovae and supernova remnants. This talk will review our basic understanding of the explosion mechanism and report some results of such observational tests. |

07. 12. 2017 at 14:00S2 11/10 | ## Theorie-SeminarAkaki Rusetsky (Uni Bonn) A detailed review of the general framework, which enables one to extract the bound-state and scattering observables in the three-particle sector from the measured three-particle energy spectrum on the lattice, is given. The framework is based on the particle-dimer formulation of the non-relativistic effective theory in a finite volume. In particular, the absence of the off-shell effects in the finite volume spectrum and the finite-volume shift of the three-particle bound state energy are discussed. Further, it is explicitly shown that, taking into account the cubic symmetry on the lattice, the three-particle quantization condition can be block-diagonalized, where the blocks correspond to the different irreducible representations of the octahedral group. |

09. 11. 2017 at 14:00S2 11/10 | ## Theorie-SeminarJoaquin Drut (UNC) Non-relativistic quantum matter, as realized in ultracold atomic gases, continues to be a remarkably versatile playground for many-body physics. Experimentalists have exquisite control over temperature, density, coupling, and shape of the trapping potential. Additionally, a wide range of properties can be measured: from simple ones like equations of state to more involved ones like the bulk viscosity and entanglement. The latter has received much attention due to its connection to quantum phase transitions, but it has proven extremely difficult to compute: stochastic methods display exponential signal-to-noise issues of a very similar nature as those due to the infamous sign problem affecting finite-density QCD. In this talk, I will present an algorithm that solves the signal-to-noise issue for entanglement, and I will show results for strongly interacting systems in three spatial dimensions that are the first of their kind. I will also present a few recent explorations of the thermodynamics of polarized matter and other cases that usually have a sign problem, using complexified stochastic quantization. |

02. 11. 2017 at 14:00S2 11/10 | ## Theorie-SeminarJacopo Ghiglieri (CERN) The addition of sterile, massive right-handed neutrinos to the Standard Model represents an economical extension with the potential of accounting for three SM shortcomings: the active (left-handed) neutrino masses and oscillations, the matter-antimatter imbalance of the universe and the nature of Dark Matter. I will start by introducing the model and reviewing the basics of the mechanisms responsible for masses, baryogenesis and DM, i.e. see-saw, leptogenesis and resonant production of keV-scale right-handed neutrinos respectively. I will then concentrate on two related ingredients for computations of leptogenesis and or/dark matter: the right-handed neutrino production rate and the lepton asymmetry washout rate, and show how they can be computed, extending to early universe cosmology techniques devised for the QCD plasma in heavy ion physics. |

26. 10. 2017 at 14:00S2 11/10 | ## SFB ColloquiumAleksi Vuorinen (Helsinki Institute of Physics) Neutron stars, currently probed using both electromagnetic and gravitational wave observations, contain some of the densest matter in the known universe, possibly including even deconfined quark matter. In my talk, I will describe recent efforts to understand the collective properties of high-density quark matter, using both resummed perturbation theory and the holographic AdS/CFT duality. Prospects for quantitatively constraining the observable properties of neutron stars using these results will also be discussed in detail. |

11. 08. 2017 at 14:00S2 11/10 | ## Theorie-SeminarSota Yoshida (University of Tokyo) The derivation of shell-model effective Hamiltonian from chiral nuclear forces based on various ways, MBPT, IM-SRG, and CC, is one of the hottest topics in nuclear structure physics. I will show the various uncertainties of shell-model interactions derived from chiral NN and 3N forces. I will discuss, in particular, the difference between ones by valence IM-SRG and MBPT and the uncertainties due to the treatment of three-body forces, then show my some results for pf-shell nuclei. |

20. 07. 2017 at 14:00S2 11/10 | ## Theorie-SeminarTim Harris (Helmholtz Institut Mainz) In this talk I will describe a new calculation of the thermal production |

13. 07. 2017 at 15:15S2 11/10 | ## SFB ColloquiumKei Kotake (Fukuoka University/Japan) We will report status of multi-messenger predictions from our 2D and 3D core-collapse supernova (SN) models. After some review about SN multi-messengers, we show that progenitor's core-compactness is a good diagnostics for predicting gravitational-wave (GW) signals and also diffuse-supernova-neutrino-background (DSNB) signals. From our 3D rotating models, we show some interesting viewing-angle effects of the neutrino and GW signals. Finally we report our on-going project to update neutrino opacities in our work-horse supernova code. |

12. 07. 2017 at 14:00S2 11/207 | ## Theorie-SeminarLennart Dabelow (Uni Jena) Using functional renormalization group methods, we investigate (2+1)-dimensional relativistic fermion systems with momentum-dependent couplings, which serve as effective theories in condensed matter or as toy models for high-energy physics. While derivative expansions of such models with pointlike interactions have been studied extensively in the literature, little is known about the vertex functions' momentum dependence. After a general analysis of momentum-dependent flow equations, we work out dominant interaction channels and determine renormalization group fixed points and critical exponents of Gross-Neveu- and Thirring-type models using pseudospectral methods. In the limit of infinite flavor number, we can even derive an analytic solution. Finally, we compare our findings to previous results obtained by different approaches. |

06. 07. 2017 at 14:00S2 11/10 | ## Theorie-SeminarTono Coello (TU Darmstadt) We studied beta decays within an effective theory that treats nuclei near the shell closures as a spherical collective core with an even number of neutrons and protons coupled to an additional neutron and/or proton. We start exploring Gamow-Teller beta decays of parent odd-odd nuclei into the ground-, one-, and two-phonon states of the daughter even-even system. The theoretical uncertainty for the matrix elements associated to these decays is estimated based on the power counting of the effective theory. For a variety of medium-mass and heavy isotopes, the theoretical matrix elements are in good agreement with experiment within the theoretical uncertainties. We then study the two-neutrino double-beta decay into ground states. Our results are also consistent with experiment within theoretical uncertainties, without the necessity to further adjust low-energy constants. |

29. 06. 2017 at 14:00S2 11/10 | ## Theorie-SeminarGeorge Bertsch (INT) Coexistence of different shapes is an old subject that advanced greatly in |

28. 06. 2017 at 11:00S2 08/171 | ## SFB ColloquiumSharon McGrayne (SFB 1245 Women's Week) When my first book Nobel Prize Women in Science was published in 1993, the legal barriers against women in academic science seemed to be fading into the past. But now we realize that subtle barriers are also difficult to deal with. In my talk, I'll give some examples, past and present, and describe recent research on the subject. In particular, I will draw on what I've learned from the writing a book about the present situation for women in science with Dr. Rita Colwell, microbiologist, former director of the National Science Foundation, and Distinguished Professor at the University of Maryland, College Park, and Johns Hopkins University. |

18. 05. 2017 at 15:30S2 11/207 | ## SFB ColloquiumPaul-Gerhard Reinhard (Uni Erlangen) Self-consistent nuclear models are based on energy-density functional adjusted to a reference set of nuclear data. The talk concentrates on the most widely used Skyrme- Hartree-Fock (SHF) approach comparing occasionally with the relativistic mean-field model. |

04. 05. 2017 at 14:00S2 11/10 | ## Theorie-SeminarCorbinian Wellenhofer (TU Muenchen) The equation of state (EoS) of hot and dense neutron-rich nuclear matter is an essential quantity in nuclear astrophysics and governs the properties of neutron stars and core-collapse supernovae. In this talk, we discuss computations of the thermodynamic nuclear EoS in many-body perturbation theory (MBPT) using nuclear two- and three-body interactions derived from chiral effective field theory. We show that the proper generalization of MBPT to finite temperatures amounts to a nontrivial reorganization of the standard linked-cluster expansion for the free energy in terms of a Legendre transformation of truncated correlation functions. Using this framework, we then investigate in detail the isospin-asymmetry dependence of the EoS at different densities and temperatures. Finally, we discuss future research efforts that are headed towards the construction of a chiral nuclear EoS for astrophysical applications. |

16. 02. 2017 at 14:00S2 11/10 | ## Theorie-SeminarJoerg Jaeckel (Uni Heidelberg) Very light bosons, produced non-thermally in the early Universe are an intriguing possibility for the cold dark matter of the Universe. Particularly interesting candidates are axions, axion-like particles and hidden photons. This talk will discuss the current status of such light dark matter with a particular emphasis towards opportunities for its detection. We also venture to some more exotic candidates and motivations. |

09. 02. 2017 at 15:15S2 11/10 | ## SFB ColloquiumThomas Luu () I discuss the application of lattice monte carlo (MC) techniques to calculate the properties of low-dimensional non-relativistic systems. For specific applications I consider the 2-dimensional graphene and quasi 1-dimensional carbon nanotube systems at half-filling with strongly correlated electrons. I compare and contrast the use of MC techniques in lattice QCD with these low-dimensional non-relativistic systems, and show how lattice QCD techniques can be applied to calculate the quasi-particle spectrum of these systems. I discuss the limitations of this formalism, and conclude with an outlook of possible future calculations. |

26. 01. 2017 at 15:15S2 11/10 | ## SFB ColloquiumBarbara Dietz (Lanzhou University/China) High resolution experiments have recently lead to a complete identification (energy, spin, and parity) of 151 nuclear levels up to an excitation Energy of Ex= 6.20 MeV in 208Pb. We present a thorough study of the fluctuation properties in the energy spectra of the unprecedented set of nuclear bound states. In a first approach we grouped states with the same spin and parity into 14 subspectra, analyzed standard statistical measures for short- and long-range correlations and then computed their ensemble average. Their comparison with a random matrix ensemble which interpolates between Poisson statistics expected for regular systems and the Gaussian Orthogonal Ensemble (GOE) predicted for chaotic systems shows that the data are well described by the GOE. In a second approach, following an idea of Rosenzweig and Porter we considered the complete spectrum composed of the independent subspectra. We analyzed their fluctuation properties using the method of Bayesian inference involving a quantitative measure, called the chaoticity parameter f, which also interpolates between Poisson (f=0) and GOE statistics (f=1). It turns out to be f~0.9. This is so far the closest agreement with GOE observed in spectra of bound states in a nucleus. The same analysis has also been performed with spectra computed on the basis of shell model calculations with different interactions (SDI, KB, M3Y). While the simple SDI exhibits features typical for nuclear many-body systems with regular dynamics, the other, more realistic interactions yield chaoticity parameters f close to the experimental values. |

22. 12. 2016 at 14:00S2 11/10 | ## Theorie-SeminarJonas Lippuner (Caltech) The Big Bang produced mostly hydrogen and helium. Nuclear fusion in |

15. 12. 2016 at 14:00S2 11/10 | ## Theorie-SeminarDaniel Robaina (TU Darmstadt) I will discuss some aspects of finite temperature calculations of Lattice gauge theories. First, I will focus on boundary effects and show how these can be used to our advantage. In particular, I will present the |

14. 12. 2016 at 13:30S2 11/207 | ## Theorie-SeminarSarah Wesolowski (Ohio State University) |

05. 12. 2016 at 15:30S2 11/10 | ## Theorie-SeminarRalf-Arno Tripolt (ECT* Trento) The RVP method in principle allows to obtain the analytic continuation of a function given in numerical form. It only requires real input in order to reconstruct the underlying function not only along the real axis but also in the complex plane. It is applied to experimental data in order to locate complex resonance poles as well as decay thresholds. Moreover, it is applied to numerical data on a Euclidean (imaginary-time) propagator in order to obtain the real-time propagator and the corresponding spectral function in momentum space. This procedure in principle represents an alternative to techniques like the Maximum Entropy Method (MEM) and to inverting the associated Laplace transform. (https://arxiv.org/abs/1610.03252) |

01. 12. 2016 at 14:00S2 11/10 | ## Theorie-SeminarThomas Duguet (CEA, Saclay) I will elaborate on the recent progress of ab initio nuclear many-body calculations focusing on the benefit of exploiting the concept of symmetry breaking (and subsequent restoration) to tackle open-shell systems. I will briefly review various recent formal developpements as well as recent and future implementations along this line. In order to illustrate some aspects of the current capacity of ab initio calculations in mid mass nuclei, I will present new results of a systematic study dedicated to the potential "bubble" nucleus 34Si. |

24. 11. 2016 at 15:20S2 11/10 | ## SFB ColloquiumPierre Capel () Away from the valley of stability, a numerous of exotic nuclear structures are encountered: shell inversions, halo nuclei,... The study of these short-lived exotic systems is mostly performed through nuclear reactions measured at Radioactive-Ion Beam facilities. To infer valuable structure information from experimental data, a reliable model of the reaction mechanism coupled to a realistic description of the nucleus under investigation is required. |

17. 11. 2016 at 14:00S2 11/10 | ## Theorie-SeminarChristian Fischer () |

10. 11. 2016 at 14:00S2 11/10 | ## Theorie-SeminarMarc Wagner () I give a brief introduction for non-experts, how to compute hadron |

03. 11. 2016 at 15:20S2 11/10 | ## SFB ColloquiumXiaofei Yang (KU Leuven) High resolution laser spectroscopy can access to multiple nuclear properties of ground/isomeric states of radioactive nuclei far from stability, such as nuclear spins, nuclear magnetic and quadruple moments and charge radii [1]. These fundamental properties of exotic nuclei provide important information for the investigation of the nuclear structure in different regions of nuclear chart. Currently, two complementary collinear laser spectroscopy set-ups are available at ISOLDE, Collinear Laser Spectroscopy (COLLAPS) and Collinear Resonant Ionization Spectroscopy (CRIS) [2]. |

20. 10. 2016 at 14:00S2 11/10 | ## Theorie-SeminarBoris Carlsson (Chalmers University) The search for a theoretical understanding of the interaction between nucleons is an ongoing challenge ever since the neutron was discovered in the 1930's. In a modern picture the strong force is a residual force stemming from QCD - the interaction between quarks and gluons. This fact can be incorporated in nucleon interaction models through the use of Chiral Effective Field Theory. Together with a power counting scheme this approach allows for calculations of low-energy two-nucleon, pion-nucleon and few-nucleon observables using the same theoretical framework. Physics that is not included explicitly in the Effective Field Theory is incorporated via a set of low-energy constants that need to be determined by a fit to experimental data. Together with ever improving ab initio many-body methods and increasing computational power, this opens up for precise theoretical predictions with a handle on the accompanying uncertainty. |

15. 09. 2016 at 14:00S2 11/10 | ## Theorie-SeminarMichael Wurm (Johannes Gutenberg University Mainz) TBA |

13. 09. 2016 at 14:00S2 11/207 | ## Theorie-SeminarMark Caprio (University of Notre Dame) Ab initio calculations of nuclear structure face the challenge of describing a complex multiscale quantum many-body system. The nuclear wave function has both strong short-range correlations and long-range contributions. Natural orbitals provide the means of adapting the single-particle basis for ab initio nuclear no-core configuration interaction (NCCI) calculations to better match the many-body wave function. Natural orbitals are obtained by diagonalizing the one-body density matrix from a calculation using an initial single-particle reference basis, such as the traditional harmonic oscillator basis. A natural orbital basis builds in contributions from high-lying oscillator shells, accelerating convergence of wave functions, energies, and other observables. This talk will provide an introduction to the use of natural orbitals in NCCI calculations. We will explore the convergence of calculated energies, radii, and electromagnetic observables in p-shell nuclei. |

08. 09. 2016 at 14:00S2 11/10 | ## Theorie-SeminarAngelo Calci (TRIUMF) The rapid developments to construct divers families of chiral two- (NN) and three-nucleon (3N) interactions and the conceptual and technical improvements of ab initio many-body approaches pose a great opportunity for nuclear physics. The accurate description of the 11Be nucleus, in particular, n+10Be halo structure and the ground-state parity inversion constitutes an enormous challenge for the developments of nuclear forces and many-body approaches. I present a sensitivity analysis of structure and reaction observables to different NN+3N interactions using the ab initio NCSM with continuum (NCSMC). The explicit inclusion of 3N interactions in ab initio reaction calculations is computationally highly demanding and constitutes the current bottle neck for the description of complex nuclear reactions. |

01. 09. 2016 at 14:00S2 11/10 | ## Theorie-SeminarSven Binder (Oak Ridge National Laboratory) We develop interactions from chiral effective field theory (EFT) that are tailored to the harmonic oscillator basis. As a consequence, ultraviolet convergence with respect to the model space is implemented by construction and infrared convergence can be achieved by enlarging the model space for the kinetic energy. By fitting to realistic phase shifts and deuteron data we construct an effective interaction from chiral EFT at next-to-leading order. Many-body coupled-cluster calculations of nuclei up to 132Sn exhibit a fast convergence of ground-state energies and radii in feasible model spaces. |

04. 08. 2016 at 14:00S2 11/10 | ## Theorie-SeminarKe-Jung Chen (National Astronomical Observatory of Japan) One of the paramount problems in modern cosmology is to elucidate how the first generation of luminous objects, stars, supernovae, accreting black holes, and galaxies, shaped the early universe at the end of the cosmic dark ages. According to the modern theory of cosmological structure formation, the hierarchical assembly of dark matter halos provided the gravitational potential wells that allowed gas to form stars and galaxies inside them. Modern large telescopes have pushed the detection of galaxies up to a redshift of z ~ 10. However, models of the first luminous objects still require considerable effort to reach the level of sophistication necessary for meaningful predictions, Due to the complexity of involved physical phenomena, this physical understanding may only come by the proper use of numerical simulations. Therefore, I have used state-of-the-art simulations on some of largest supercomputers to study these objects. In my talk, I will discuss the possible physics behind the formation of these first luminous objects by presenting the results from our simulations. I will also give possible observational signatures of the cosmic dawn that will be the prime targets for the future telescopes such as the James Webb Space Telescope (JWST). |

28. 07. 2016 at 14:00S2 11/10 | ## Theorie-SeminarMirko Miorelli (TRIUMF) The electric dipole polarizability quantifies the low-energy behavior of the dipole strength. It is related to the proton and neutron distributions of the nucleus, and thereby can be used to constrain the neutron equation of state and the physics of neutron stars. Only recently however, new developments in ab initio methods finally allowed first principles studies of the dipole strength in medium-mass nuclei [1,2,3]. Using the Lorentz integral transform coupled cluster method with the newly developed chiral interaction at next-to-next-to-leading order (NNLO_sat) we study the low energy behavior of the dipole strength in 4He, 16O, 22O [3] and 48Ca for which the polarizability has been recently measured by the Osaka-Darmstadt collaboration. For the exotic 22O we observe large contribution to the dipole strength at very low energy, indicating the presence of a pygmy dipole resonance, in agreement with what experimentally found by Leistenschneider et al.[4]. Finally, I will show preliminary calculations on the exotic 8He, which exhibits extremely large dipole polarizability and neutron skin. |

19. 07. 2016 at 14:00S2 11/207 | ## Theorie-SeminarAlan A. Dzhioev (JINR, Dubna) The significant role played by processes with neutrinos in core-collapse supernovae is well known. At densities of rho > 10^11 g cm^-3 neutrino interactions with matter become important, leading to neutrino trapping and thermalization. Moreover, neutrino energy deposition behind the stalled shock may play a crucial role in successful explosion. |

19. 07. 2016 at 12:00S2 11/10 | ## Lunch Club SeminarThorben Graf (SUBATECH, Nantes) Results for several thermodynamic quantities within the next-to-leading order calculation of the thermodynamic potential in perturbative QCD at finite temperature and chemical potential including non-vanishing quark masses are presented. These results are compared to lattice data and to higher-order optimized perturbative calculations to investigate the trend brought about by mass corrections. Furthermore, the findings of the investigation of the thermodynamics at nonzero isospin density for cold QCD are also presented. |

14. 07. 2016 at 14:00S2 11/10 | ## SFB Colloquium (Argonne National Laboratory) The atomic structure of simple, few electron systems can be precisely calculated. Likewise, few nucleon systems can be accurately treated within ab-initio nuclear theories. Bringing these two fields together, we perform precision studies of light, radioactive isotopes that show a remarkable range of neutron-to-proton ratios. Techniques of high-resolution laser spectroscopy and of laser cooling and trapping offer unique access to precision nuclear structure and weak interaction studies of these isotopes to probe nucleon-nucleon interactions and to search for physics beyond the Standard Model. In my talk I will cover two on-going efforts in this direction: precision measurements of nuclear charge radii moving towards the proton rich Boron-8 and a beta-neutrino angular correlation measurement with laser trapped Helium-6. |

07. 07. 2016 at 14:00S2 11/10 | ## Theorie-SeminarMartin Obergaulinger (Universidad de Valencia) Across the wide range of possible progenitors, supernova core collapse |

30. 06. 2016 at 14:00S2 11/10 | ## Theorie-SeminarIrene Tamborra (Niels Bohr Institute) Neutrinos are key particles in core-collapse supernovae. Neutrinos can be direct probes of the still uncertain and fascinating supernova mechanism. Intriguing recent developments on the role of neutrinos during the stellar collapse are reviewed, as well as our current understanding of the flavor conversions in the stellar envelope. The detection perspectives of the next burst will be also outlined. |

28. 06. 2016 at 15:00S2 11/207 | ## Theorie-SeminarIngo Tews (Institute for Nuclear Theory, Seattle) |

23. 06. 2016 at 14:00S2 11/10 | ## Theorie-SeminarLucas Platter (University of Tennessee) Halo nuclei are weakly bound nuclei whose degrees of freedom are a |

09. 06. 2016 at 14:00S2 11/10 | ## Theorie-SeminarTakami Kuroda (Uni Basel) |

02. 06. 2016 at 14:00S2 11/207 | ## Theorie-SeminarHermann Krebs () Nuclear forces and currents serve as an input for various many-body calculations of nuclear spectra and scattering processes. Their quantitative description without losing the connection to QCD is provided by a powerful tool like chiral effective field theory. In my talk I will discuss the current status of their construction and their ongoing implementations. In particular I will present our results on two-nucleon axial vector current upto leading one-loop order in chiral expansion which is consistent with already developed N3LO nuclear forces, is renormalizable and behaves as a four vector under Lorentz transformation. Due to upsense of short-range low energy constants at this order the current has high predictive power. |

03. 05. 2016 at 14:00S2 11/10 | ## Theorie-SeminarChristian Forssen (Chalmers University) Ab initio nuclear models are required for a truly predictive theory of nuclei and their interactions with external probes. However, true predictive power requires the ability to quantify theoretical uncertainties. While it is true that theoretical error estimates are difficult to obtain, the pursuit thereof plays a pivotal role in science. Reliable theoretical errors can help to determine to what extent a disagreement between experiment and theory hints at new physics, and they can provide input to identify the most relevant new experiments. As will be shown, nuclear theory has reached a stage where such questions can be addressed. |

26. 04. 2016 at 12:00S2 11/10 | ## Lunch Club SeminarStefano Carignano (INFN Gran Sasso ) We study the thermodynamic properties of matter at vanishing temperature for non-extreme values of the isospin chemical potential and of the strange quark chemical potential. From the leading order pressure obtained by maximizing the static chiral Lagrangian density we derive a simple expression for the equation of state in the pion condensed phase and in the kaon condensed phase. We find an analytical expression for the maximum of the ratio between the chiral perturbation energy density and the Stefan-Boltzmann energy density as well as for the isospin chemical potential at the peak in good agreement with lattice simulations of quantum chromodynamics. We speculate on the location of the crossover from the Bose-Einstein condensate state to the Bardeen-Cooper-Schrieffer state by a simple analysis of the thermodynamic properties of the system. For isospin chemical potetials greater or equal 2 m_pi the leading order chiral perturbation theory breaks down; as an example it underestimates the energy density of the system and leads to a wrong asymptotic behavior. |

22. 04. 2016 at 14:45S2 11/10 | ## Theorie-SeminarMichael Urban (IPN Orsay) In the inner crust of neutron stars, nuclei (clusters) are immersed in a dilute gas of unbound neutrons. At the typical temperatures of neutron stars, the neutrons are superfluid and the most important excitations are therefore phase fluctuations of the gap (Goldstone mode or Bogoliubov-Anderson sound). In the first part of the talk, I will discuss the Goldstone mode in uniform neutron matter and its contribution to the specific heat obtained within the Quasiparticle Random-Phase Approximation (QRPA) and compare it with results of simple superfluid hydrodynamics. In the second part, the hydrodynamic approach will be applied to the inhomogeneous crust (crystalline and pasta phases) to calculate the effective mass of the clusters and the density of superfluid neutrons. Consequences for the interpretation of glitch data will be discussed. |

22. 04. 2016 at 14:00S2 11/10 | ## Theorie-SeminarMicaela Oertel (LUTH, CNRS/Observatoire de Paris, Meudon) To explain observations of overluminous Type Ia supernovae, strongly magnetized super-Chandrasekhar mass white dwarfs have been proposed as their progenitors. This has interesting implications in high-precision cosmology, as Type Ia supernovae have been widely used as standard candles. To compute equilibrium configurations of magnetized white dwarfs, we apply our recently developed self-consistent formalism for modelling the macroscopic structure of a compact object in strong magnetic fields. In previous attempts to determine the mass-radius relation of magnetized white dwarfs, there has been no study which simultaneously included Landau quantization of electrons in a strong magnetic field, electron-ion interactions and effects of pressure anisotropy due to the breaking of spherical symmetry by the background magnetic field. In addition to a self-consistent modelling of the structure of a white dwarf in strong magnetic fields in full general relativity, we perform a systematic study of its stability which ultimately decides whether such objects can exist in nature. We confirm previous speculations that indeed the onset of electron captures and pycnonuclear reactions limit the stability of strongly magnetized white dwarfs and hence they cannot explain the observations of overluminous supernovae. |

21. 04. 2016 at 14:00S2 11/10 | ## Theorie-SeminarEdmond Iancu (IPhT - CEA) For an energetic jet propagating through a weakly-coupled quark-gluon plasma, I present the physical picture of jet quenching, as emerging from the interplay between multiple branchings and elastic collisions. The medium-induced branchings are quasi-democratic and lead to a phenomenon of wave turbulence, which ensures the efficient transmission of the energy from the leading particle to a myriad of soft particles. The elastic collisions are responsible for the momentum broadening and the thermalization of the soft branching products. This first-principle picture provides a natural explanation for the phenomenon of di-jet asymmetry observed in Pb+Pb collisions at the LHC. |

14. 04. 2016 at 14:00S2 11/10 | ## Theorie-SeminarSamuel Jones (University of Victoria) |

10. 03. 2016 at 14:00S2 11/10 | ## Theorie-SeminarVittorio Soma (CEA Saclay) After several developments in terms of many-body techniques have pushed ab initio nuclear structure calculations to cover a good fraction of existing mid-mass nuclei, recently the focus of practitioners has moved back to the input nuclear Hamiltonian. Employing one of such many-body techniques, namely self-consistent Green functions, and different state-of-the-art two- and three-nucleon interactions, I will discuss novel ab initio results for oxygen, potassium, calcium and nickel isotopic chains. Particular attention will be dedicated to the performance of a newly developed interaction, NNLOsat. In the case of oxygens I will also present a new re-evaluation of matter radii that complements well-known energy systematics. |

18. 02. 2016 at 14:00S2 11/10 | ## Theorie-SeminarRiccardo Ciolfi (University of Trento) Recent observations indicate that in a large fraction of binary neutron star (BNS) mergers a long-lived neutron star (NS) may be formed rather than a black hole. Unambiguous electromagnetic (EM) signatures of such a scenario would strongly impact our knowledge on how short gamma-ray bursts (SGRBs) and their afterglow radiation are generated. Furthermore, such EM signals would have profound implications for multimessenger astronomy with joint EM and gravitational-wave (GW) observations of BNS mergers, which will soon become reality with the first science runs of the advanced LIGO/Virgo network of ground-based GW detectors already on the way. I will discuss various aspects of BNS mergers leading to the formation of a long-lived NS, including the scenarios that relate such mergers to SGRBs. Moreover, I will introduce a new model to follow the post-merger evolution of the system and to predict in a self-consistent way the (X-ray) emission powered by the NS spindown. I will present the computed lightcurves and spectra and discuss these results in the context of SGRBs and multimessenger astronomy. |

04. 02. 2016 at 14:00S2 11/10 | ## Theorie-SeminarWilliam J. Porter (UNC, Chapel Hill) Studying entanglement in many-body quantum systems is an active and exciting area of research with several key quantities only recently becoming experimentally accessible. In my talk, I will discuss the basic definition for and some lattice Monte Carlo approaches to computing the Renyi entanglement entropies for strongly interacting fermions. With the introduction of an auxiliary parameter, a well-known signal-to-noise problem can be circumvented, and the Renyi entropies can be computed using auxiliary field Monte Carlo methods. After presenting proof-of-principle results for small systems, I will comment on my progress toward characterizing universal entanglement properties of the scale-invariant Fermi gas. |

02. 02. 2016 at 14:00S2 11/207 | ## Theorie-SeminarAkaki Rusetsky (University of Bonn) I review the use of the effective field theory methods in a finite volume for the study of hadron-hadron scattering processes on the lattice. For illustration of the general approach, two examples are given. We first consider inelastic scattering processes and show that one can directly extract the scattering phase and the inelasticity parameter on the lattice without studying scattering into all open channels separately. The approach is applicable even in the presence of the multi-particle (three and more) inelastic channels. Next, an explicit expression for the energy-level shift of a shallow bound state of three identical particles in a finite volume is derived. It is demonstrated that measuring the volume-dependence of the spectrum of the bound states provides one with an important information about their nature. |

28. 01. 2016 at 14:00S2 11/10 | ## Theorie-Seminar (University of Tennessee) Previously, collective motion in heavy nuclei has been studied within collective and algebraic models. While they reproduce the energy spectra of these systems, their predictions for electromagnetic transitions and moments are in disagreement with experimental data. An effective field theory approach to collective motion in heavy nuclei solves this long-standing problem. The systematic construction of the theory allows for the estimation of theoretical uncertainties. Bayesian methods can be employed to quantify these uncertainties, providing a clear statistical interpretation. Experimental data is consistent with the theory within theoretical uncertainties. The systematic construction of the electric quadrupole operator allows for the description of faint interband transitions strengths in rotational nuclei and large static quadrupole moments in vibrational nuclei near shell closures. |

10. 12. 2015 at 14:00S2 11/10 | ## Theorie-SeminarCristina Volpe (APC, Paris) |

08. 12. 2015 at 14:00S2 11/207 | ## Theorie-SeminarDario Vretenar (University of Zagreb) Low-energy collective excitations reflect the underlying effective nuclear interactions and shell structure of single-nucleon orbitals. The evolution of collective states characterizes a variety of interesting structure phenomena across the nuclide chart: clustering in light nuclei, modification of shell structures and occurrence of deformations, location of the drip-line in neutron-rich nuclei, shape coexistence and shape transitions in medium heavy and heavy nuclei, low-energy resonances, octupole correlations, subshell closures in superheavy nuclei, etc. |

03. 12. 2015 at 14:00S2 11/10 | ## Theorie-SeminarSean M. Couch (MSU) Core-collapse supernovae are the luminous explosions that herald the death of massive stars. While core-collapse supernovae are observed on a daily basis in nature, the details of the mechanism that reverses stellar collapse and drives these explosions remain unclear. While the most recent high-fidelity simulations show promise at explaining the explosion mechanism, there remains tension between theory and observation. This is likely telling us we are missing important physics in our simulations. I will discuss some interesting candidates for such missing physics that could be crucial to the supernova mechanism. In particular, I will describe our efforts to develop more realistic initial conditions for supernova simulations with fully 3D massive stellar evolution calculations. Such realistic 3D initial conditions turn out to be favorable for successful explosions, in large part because they result in stronger turbulence behind the stalled supernova shock. I will also discuss the important role turbulence is playing in the supernova mechanism and what might be required for accurately modeling the turbulence in our simulations. |

26. 11. 2015 at 14:00S2 11/10 | ## Theorie-SeminarMirko Miorelli (TRIUMF) The study of electromagnetic break-up reactions with nuclei is of fundamental importance to understand nuclear dynamics. In particular, ab initio approaches are crucial to connect nuclear physics with the more fundamental QCD regime. Until very recently, most of the ab initio calculations of such reactions where the nucleus is broken in several pieces, were restricted to very light nuclei (A<=7). I will show how the coupled-cluster method and the Lorentz integral transform are combined for the computation of inelastic reactions into the continuum for medium-mass nuclei [1]. I will discuss results for the photo-absorption cross section for a variety of nuclei, in particular for the neutron rich 22O nucleus where we find a low-lying E1 strength which compares fairly well with experimental data from GSI [2]. I will then focus on the calculation of the electric dipole polarizability showing results for 4He, 16O and 40Ca. Exploring the correlation between the electric dipole polarizability and the charge radius I will show how we make predictions for the electric dipole polarizability of Ca48 [3] and Ni68. |

19. 11. 2015 at 14:00S2 11/10 | ## Theorie-SeminarJacobo Ruiz de Elvira (Bonn University) A precise understanding of low-energy pion-nucleon interactions is central for many areas in nuclear and hadronic physics, ranging from the scalar couplings of the nucleon to the long-range part of two-pion-exchange potentials and three-nucleon forces in Chiral Effective Field Theory. We present a calculation that combines the general principles of analyticity, unitarity, and crossing symmetry with modern high-precision data of hadronic atoms, leading to a phenomenological description of the pion-nucleon amplitude with unprecedented rigor and accuracy. Consequences for the pion-nucleon sigma-term and the matching to Chiral Perturbation Theory will be discussed. |

29. 10. 2015 at 14:00S2 11/10 | ## Theorie-SeminarRaju Venugopalan (BNL/Heidelberg) A future Electron-Ion Collider will have about 1000 times the luminosity of HERA and can be used to study the short distance properties of (polarized) light and heavy nuclei. We outline a specific measurement which illustrates the potential of such a machine to uncover the quark and gluon nature of short range nucleon-nucleon interactions. |

22. 10. 2015 at 14:00S2 11/10 | ## Theorie-SeminarYudai Suwa (Kyoto University) A core-collapse supernovae is a generation site of a neutron star as well as one of the largest explosions in the universe. In this talk, I will show our recent results with multi-dimensional neutrino-radiation hydrodynamics simulations, especially focusing on neutron star formation. |

15. 10. 2015 at 14:00S2 11/10 | ## Theorie-SeminarJesus Casal (Universidad de Sevilla) Over the last decades, the advances in radioactive ion beam facilicies have expanded our knowledge of nuclear physics. The structure of weakly-bound and exotic nuclei near the neutron and proton driplines have motivated comprehensive theoretical studies and experimental efforts. In particular, several interesing features, such as few-body structures, clusterization or nuclear halos, have been observed for weakly-bound light nuclei. The case of three-body systems (such as 6He, 9Be, 11Li or 17Ne) and their implications in nuclear reactions and nucleosynthesis processes will be discussed. |

04. 08. 2015 at 14:00S2 11/10 | ## Theorie-SeminarHeiko Hergert (NSCL/ Michigan State University) Nowadays, advances in many-body theories and their numerical implementation have made it possible to routinely calculate properties of nuclei in the mass A~100 region from first principles. The In-Medium Similarity Renormalization Group (IM-SRG), in particular, provides access to open-shell nuclei, either directly or through the auxiliary step of deriving valence-space interactions for use with existing Shell Model technology. |

30. 07. 2015 at 14:00S2 11/10 | ## Theorie-SeminarAlexander Heger (Monash Centre for Astrophysics, Monash University, Australia) The first stars are unique not only in being first but also because of |

20. 07. 2015 at 14:00S2 15/134 | ## DoktorprüfungDavid Scheffler (TU Darmstadt) |

20. 07. 2015 at 11:00S2 11/10 | ## Theorie-SeminarNoemi Rocco () |

14. 07. 2015 at 14:00S2 11/10 | ## Dense Matter SeminarDaniel Nowakowski (TU Darmstadt) |

02. 07. 2015 at 14:00S2 11/10 | ## Theorie-SeminarRaphael Hix (University of Tennessee) Core-collapse supernovae (CCSNe), the culmination of massive stellar evolution, are the principle actors in the story of our elemental origins. Though brought back to life by neutrino heating, the development of the supernova is inextricably linked to three-dimensional fluid flows, with large scale hydrodynamic instabilities allowing successful explosions that spherical symmetry would prevent. The importance of the neutrino interactions and the three-dimensional fluid flows that they drive have often been ignored when the nucleosynthesis that occurs in these explosions, and their resulting impact on galactic chemical evo- lution, is discussed. I will present results from simulations of successful explosions using our CHIMERA code, and discuss how the multidimensional character of the explosions directly impacts the development of the explosion as well as the nucleosynthesis and other observables of core-collapse supernovae. |

24. 06. 2015 at 14:00S2 11/10 | ## Theorie-SeminarNorbert Kaiser () |

23. 06. 2015 at 12:00S2 11/10 | ## Lunch Club SeminarStefano Carignano (University of Texas at El Paso) What are the properties of cold and dense quark matter? How is chiral symmetry restored at low temperatures and finite densities? While the next generation of heavy-ion experiments might help shed some light on this region of the QCD phase diagram, at the moment compact stellar objects provide the only known realization in nature of these extreme conditions. In this talk, I will show how the formation of inhomogeneous chiral symmetry breaking phases affects the equation of state of dense quark matter, and its consequences on the resulting mass-radius sequences for compact stars. I will also discuss the influence of a background magnetic field, which is shown to alter qualitatively the energy spectrum of inhomogeneous quark matter through the generation of an anomalous term. A similar situation occurs when dealing with a particular kind of inhomogeneous one-dimensional solution, namely a plane wave modulation called ``chiral spiral'' which arises naturally in QCD in the limit of of a large number of colors. If time allows, I will discuss the analogies between these two scenarios, and the difficulties arising when dealing with them in a 3+1-dimensional non-renormalizable model. |

03. 06. 2015 at 10:00S2 15/134 | ## DoktorprüfungRalf-Arno Tripolt (TU Darmstadt) |

28. 05. 2015 at 14:00S2 11/10 | ## Theorie-SeminarKuo-Chuan Pan (Basel University) The neutrino mechanism of core-collapse supernova is investigated via non-relativistic, multi-dimensional, neutrino radiation-hydrodynamic simulations. For the transport of electron flavor neutrinos, we use the interaction rates defined by Bruenn (1985) in collaboration with the isotropic diffusion source approximation (IDSA) scheme, which decomposes the transported particles into trapped particle and streaming particle components. Heavy neutrinos are described by a leakage scheme. Unlike the "ray-by-ray'' approach in other multi-dimensional IDSA implementations in spherical coordinates, we use 2D cylindrical and 3D Cartesian coordinates and solve the trapped particle component in multiple dimensions, improving the proto-neutron star resolution and the neutrino transport in angular and temporal directions. We perform Newtonian 1D-3D ab initio simulations from prebounce core collapse to several hundred milliseconds postbounce with progenitors from Woosley et al. (2002) with the HS(DD2) equation of state. We obtain robust explosions with diagnostic energies ~0.1-0.5 B for all considered 2D models within approximately 100-300 milliseconds after bounce and find that explosions are mostly dominated by the neutron-driven convection, although standing accretion shock instabilities are observed as well. We also find that the level of electron deleptonization during collapse dramatically affects the postbounce evolution, e.g. the ignorance of neutrino-electron scattering during collapse will leads to a stronger explosion. |

16. 04. 2015 at 14:00S2 11/10 | ## Theorie-SeminarDr. Pierre Capel () Coulomb breakup has been proposed as an indirect method to deduce the cross section of radiative captures of astrophysical interest [1]. In Coulomb breakup, the projectile dissociates into lighter fragments through its interaction with a heavy (high Z) target. Assuming the dissociation to be due to the sole Coulomb interaction, the reaction can be described as an exchange of virtual photons between the projectile and the target. It can thus be seen as the time-reversed reaction of the radiative capture of the fragments, which should enable us to deduce easily the radiative-capture cross section from breakup measurements [1]. |

08. 01. 2015 at 14:00S2 11/10 | ## Theorie-SeminarPanagiota Papakonstantinou (Institute for Basic Science, RISP, South Korea) A strong isoscalar dipole transition is known to be excited in a variety of nuclei, including isospin symmetric ones, at approximately 6-7 MeV. A series of theoretical studies and accumulating experimental evidence support an interpretation of the above dipole transition as an elementary surface vibration. Such a mode is potentially as interesting as any collective excitation for a variety of reasons. In addition, though, it is found to account for the observed isoscalar segment of pygmy dipole strength. |

19. 12. 2014 at 13:30S2 11/10 | ## Lunch Club SeminarLukas Holicki (TU Darmstadt) tba |

19. 12. 2014 at 11:30S2 11/207 | ## Theorie-SeminarAndreas Bauswein (Aristotle University of Thessaloniki) TBA |

17. 12. 2014 at 11:00S2 11/207 | ## Theorie-SeminarAndreas Crivellin (CERN Theory Division) In this talk I review the effective field theory approach to physics |

16. 12. 2014 at 14:00S2 11/10 | ## Theorie-SeminarKyle Wendt (University of Tennessee) Modern ab initio calculations of light and medium mass nuclei have reached a point of unprecedented precision by combining low momentum interactions from chiral effective field theory softened using renormalization group techniques. However, thorough descriptions of uncertainty in such calculations is lacking, both with respect to the many-body method employed and with respect to the systematics of the underlying Hamiltonian. This is exacerbated by many chiral interactions failing to correctly describe medium mass nuclei, often over binding while failing to correctly predict nuclear densities. I will present recent progress in quantifying errors in nuclear Hamiltonians as well as an alternative approach to constraining chiral Hamiltonians such that predictive calculations of light and medium mass nuclei are within reach. I will also present recent developments on understanding certain forms of error that enter into many calculations of light nuclei. |

26. 11. 2014 at 14:00S2 11/207 | ## Theorie-SeminarOwe Philipsen () At finite baryon density the fermion determinant of the QCD partition function is complex-valued. This so-called sign problem |

11. 11. 2014 at 14:00S2 11/10 | ## Theorie-SeminarBruno Giacomazzo (University of Trento) In this talk I will present results of fully general relativistic simulations of binary neutron star (BNS) mergers and discuss their connection with current and future astrophysical observations. BNSs are one of the most promising sources of gravitational waves (GWs) that we expect to detect in the next few years with advanced LIGO and Virgo. But they may also emit powerful electromagnetic signals and they are expected to be behind the engine powering short gamma-ray bursts (SGRBs). During the first part of the talk I will discuss the role of BNS merger simulations in predicting the gravitational wave signal emitted during the merger and its connection with the equation of state of NS matter. In the second part I will instead discuss in detail the possible connection between the central engine of SGRBs and the merger of magnetized neutron stars, both in the case in which a black hole is promptly formed after merger and in the case of the formation of a magnetar. |

07. 11. 2014 at 16:00S2 11/207 | ## Theorie-SeminarJuan Torres-Rincon (Subatech, Nantes) The Nambu-Jona-Lasinio model is an effective theory of QCD for low-energy quark interactions. I will explain how to use this model (and its extension, the Polyakov-NJL model) in combination with the Bethe-Salpeter equation, to describe mesons and diquarks as bound states of quarks + (anti)quarks. In a similar context, baryons can also be modelized as bound states of diquarks + quarks. I will present our results for the baryon masses as a function of temperature and chemical potential, and show a clear evidence of a flavor dependence of the baryon melting temperature, as suggested by experimental results in heavy-ion collisions, and supported by recent lattice-QCD results. |

07. 11. 2014 at 12:00S2 11/207 | ## Lunch Club SeminarAnton Cyrol (TU Darmstadt) We report on a self-consistent solution of the Landau gauge four-gluon vertex DSE. Our calculation includes all perturbatively leading one-loop diagrams, which constitutes the state-of-the-art truncation. As only input we use results for lower Green functions from previous Dyson-Schwinger studies that are in good agreement with lattice results. Within the truncation, no higher Green functions, which would have to be modelled, enter. Hence, the results depend only indirectly on models of Green functions. Our self-consistent solution resolves the full momentum dependence of the four-gluon vertex but is limited to the tree-level tensor structure. We calculate a few exemplary dressings of other tensor structures and find that they are suppressed compared to the tree-level structure except for the deep infrared where they diverge logarithmically. We employ the results to derive a running coupling. Furthermore, we study the coupled system of the three- and the four-gluon vertices to reduce the model dependence and to explore the convergence of the system of DSEs within the truncation scheme employed. For the scaling solution we establish a solution of the coupled system of vertices which provides promising evidence for the convergence. |

03. 11. 2014 at 13:00S2 11/207 | ## Theorie-SeminarHans-Peter Pavel (HU-Berlin and JINR Dubna) |

30. 10. 2014 at 14:00S2 11/10 | ## Theorie-SeminarMichael Urban (IPN Orsay) |

28. 10. 2014 at 12:00S2 11/10 | ## Lunch Club SeminarMicaela Oertel (LUTH, CNRS/Observatoire de Paris, Meudon ) |

23. 10. 2014 at 14:00S2 11/10 | ## Theorie-SeminarMaxwell T. Hansen (University of Washington) Numerical Lattice QCD calculations are necessarily performed in a finite volume, and for any given observable it is important to understand this constraint. Over a decade ago Lellouch and Luescher derived a relation between finite-volume matrix elements and observable decay amplitudes for the weak decay K->pi pi. The result is non-trivial, depending not only on the finite volume but also on the phase-shift of pi pi elastic scattering. In this talk we present a generalization of the Lellouch Luescher approach to study one-to-two transition amplitudes. Using a generic relativistic field theory and working to all orders in perturbation theory, we derive a master equation relating finite-volume matrix elements to physical transition amplitudes. Our derivation accommodates external currents which inject momentum, energy and angular momentum into the system. The result is applicable to systems with any number of strongly coupled two-scalar channels, and we illustrate how it can be applied to certain key examples, including heavy meson decays and meson photo production. |

07. 10. 2014 at 14:00S2 11/10 | ## Theorie-SeminarJames Lattimer (Stony Brook) |

11. 09. 2014 at 14:00S2 11/10 | ## Theorie-SeminarYang Sun (Shanghai Jiaotong University) Theoretical calculation of nuclear matrix element for Gamow-Teller type transition is important for nuclear structure, nuclear astrophysics, and fundamental physics. It is of particular interest when a laboratory measurement for weak interaction rates is impossible and the conventional shell model calculations are not feasible. |

10. 09. 2014 at 14:00S2 11/10 | ## Theorie-SeminarJoel Lynn (Los Alamos National Laboratory) |

02. 09. 2014 at 12:00S2 11/10 | ## Lunch Club SeminarMathias Wagner (Indiana University, Bloomington) Fluctuations of conserved charges (baryon number, electric charge, strangeness, charm) have proven to be a valuable tool for the investigation of the QCD phase structure. They are available from Lattice QCD simulations and can also be measured experimentally at heavy-ion colliders like RHIC and LHC. I will provide an overview of the recent process on understanding QCD thermodynamics made by the BNL-Bielefeld-CCNU collaboration using fluctuation data. |

19. 08. 2014 at 12:00S2 11/10 | ## Lunch Club SeminarAxel Maas (Jena/Graz) Yang-Mills-Higgs theory offers a rich set of physics. In particular, in some region of its parameter space it has QCD-like behavior, while in some other range it is Higgs-like. Furthermore, for the choice of the gauge group SU(2) and an SU(2) Higgs flavor symmetry it is the Higgs sector of the standard model. Therefore, it is possible to study a plethora of phenomena within a single theory. |

14. 08. 2014 at 16:00S2 11/10 | ## Theorie-PalaverDominik Smith (TU Darmstadt) The goal of the seminar is to present the motivation for lattice field theorists and high-energy physicists to study graphene, then present a step-by-step derivation of the theoretical basis of Hybrid-Monte-Carlo simulations of graphene and then give an overview over results obtained. |

14. 08. 2014 at 14:00S2 11/10 | ## Theorie-Seminar (The Ohio State University) |

17. 07. 2014 at 14:00S2 11/10 | ## Theorie-SeminarAndreas Metz (Temple University) Transverse single-spin asymmetries have been observed in a number of hard scattering processes. While the effects can be quite large, their description in terms of perturbative QCD is challenging. On the other hand, these asymmetries allow us to explore new territories in QCD. In this talk, I briefly review several key aspects of this field and also discuss some recent progress. |

16. 07. 2014 at 15:15S2 11/10 | ## Theorie-SeminarIgor Boettcher () Transverse single-spin asymmetries have been observed in a number of hard scattering processes. While the effects can be quite large, their description in terms of perturbative QCD is challenging. On the other hand, these asymmetries allow us to explore new territories in QCD. In this talk, I briefly review several key aspects of this field and also discuss some recent progress. We investigate how the reduction of spatial dimension influences superfluidity of two-component fermions in the BCS-BEC crossover from both a theoretical and an experimental perspective. The Functional Renormalization Group allows to study the system over the whole parameter space of interaction strength, density, temperature, spin-imbalance, and dimension. The high precision and tunability of recent experiments allows for a solid benchmarking of our description. In particular, recent measurements on the 2D BCS-BEC Crossover in the Jochim group at Heidelberg yield major insights into the physics of this system. We present theoretical and experimental results on the equation of state and the phase diagram as a function of dimension. |

10. 07. 2014 at 14:00S2 11/10 | ## Theorie-SeminarDaniel Phillips (Ohio University) I discuss recent work our group has undertaken on effective-field-theory (EFT) analyses of experimental data pertaining to one- and two-nucleon halos. The cases of Carbon-19 and Lithium-8 (one-neutron halos), Boron-8 (one-proton halo, and Carbon-22 (two-neutron halo) will be discussed. For the one-nucleon halos electromagnetic processes will be discussed (Coulomb dissociation and radiative capture respectively). In the case of Carbon-22 I show how the measured matter radius can be used to derive constraints on the two-neutron separation energy of this very neutron-rich system. If time permits I will also show preliminary results on Coulomb dissociation of this nucleus. In every case I show how the "Halo EFT" correlates different experimental observables with one another, in a model-independent manner, and up to an accuracy that is determined by the separation of scales in the halo system. |

03. 07. 2014 at 14:00S2 11/10 | ## Theorie-SeminarArianna Carbone (TU Darmstadt) The properties of symmetric nuclear and pure neutron matter are investigated within the self consistent Green's function method. This approach has been recently extended to include the effects of three-body forces. We employ this improved formalism to analyze the effect of many-body forces in the ladder approximation for the study of infinite nuclear matter. The three-body interaction is incorporated by means of a density dependent two-body force. This force is obtained via a correlated average over the third particle, which corresponds to using an in-medium propagator consistent with the many-body calculation we perform. Microscopic as well as bulk properties will be presented, focusing on the modications introduced by the density dependent two-body force. |

02. 07. 2014 at 14:00S2 11/207 | ## Theorie-Seminar (Monash University) Core-collapse supernovae are a challenging problem on the crossroads of astrophysics, nuclear and particle physics, and gravitational physics. They reveal themselves through a variety of observational signatures -- not only through the brilliant optical outburst, but also by their nucleosynthetic footprint, and by neutrinos and (though yet to be detected) by gravitational waves emitted from the supernova core. With the supernova engine hidden deep inside the stellar core from direct optical observations, our theoretical understanding of these events relies strongly on first-principle hydrodynamic simulation, which have recently become available in three dimensions (3D). As I shall demonstrate in this talk, these new simulations challenge many of our established views on the supernova explosion mechanism, but could also add an extremely interesting twist to nucleosynthesis processes in supernovae. |

01. 07. 2014 at 14:00S2 11/10 | ## Theorie-SeminarRaju Venugopalan (BNL) |

24. 06. 2014 at 12:00S2 11/10 | ## Lunch Club SeminarAchim Heinz (Frankfurt) The requirement of the chiral condensate to be constant over space is too restrictive. In this talk we present two recent studies on the subjects. |

17. 06. 2014 at 12:00S2 11/10 | ## Lunch Club SeminarChristoph Kommer (Heidelberg) The understanding of analytical methods in nonlinear structure formation in cosmology is highly important when considering alternatives to numerical simulations in order to obtain reliable results on sufficiently small scales or even to eventually explain scalings like the NFW profile from simulations fundamentally. Without referring to standard perturbation theory techniques in the first place one obtains fully resummed evolution equations for n-point propagators out of equilibrium. Using preliminiaries from statistical field theory a generating functional is constructed from which the desired correlators are obtained by functional differentiation assuming a Vlasov-Poisson system. Via functional methods such as the renormalization group, Schwinger-Keldysh contours or a 2PI effective action functional one in the end obtains a formally closed set of equations at second order in the correlators using a cubic action in the case of gravitational instabilities. |

16. 06. 2014 at 14:00S2 11/10 | ## Theorie-SeminarBaha Balantekin (University of Wisconsin-Madison) In a core-collapse supernova nearly all the gravitational binding energy of the progenitor star is deposited in the proto-neutron star which cools |

10. 06. 2014 at 12:00S2 11/10 | ## IKP SeminarProf. Michael Kohl (Jefferson Lab) The proton is not an elementary particle but has a substructure |

03. 06. 2014 at 12:00S2 11/10 | ## Lunch Club SeminarFederico Marquez (Santiago de Chile) |

27. 05. 2014 at 14:00S2 11/10 | ## Theorie-SeminarCaroline Robin (CEA) Self-consistent methods and Configuration-Interaction techniques are among the most used and powerful approaches to the description of many-body nuclear systems. Based on different philosophies, they differ in their domain of applicability. |

20. 05. 2014 at 10:00S2 14/024 | ## Theorie-SeminarGuy Moore (McGill University) Quantum Chromodynamics (QCD) is the theory underlying the strong interactions. Heavy ion collisions are probing QCD in a new hot many-body regime, whose interpretation requires a dialogue between experiment and theory. I will discuss our theoretical understanding of hot many-body QCD, focusing on transport phenomena and hydrodynamics. In particular, I will discuss the use and limits of perturbation theory. |

19. 05. 2014 at 09:00S2 11/10 | ## Theorie-SeminarJiunn-Wei Chen (National Taiwan University) Seeing the microscopic quantum physics in the macroscopic world is challenging, intriguing but possible! In efforts to uncover how the microscopic effect of quantum axial anomaly can show up in a macroscopic fluid, two seemingly very different approaches using the Wigner function and Berry phase were developed. We show in this talk that they are actually identical. |

06. 05. 2014 at 13:00S2 11/10 | ## Theorie-SeminarCarsten Urbach () The field of lattice QCD has seen significant advances over the last few years. This concerns in particular the inclusion of dynamical quark degrees of freedom in the simulations. We will discuss recent results obtained from simulations with mass degenerate up and down quarks and physical strange and charm. We will focus on the physics of the eta and eta' meson system and the axial U(1) problem and pi-pi scattering. |

05. 05. 2014 at 13:00S2 11/10 | ## Theorie-SeminarJohanna Erdmenger (Max-Planck-Institut) |

05. 05. 2014 at 09:00S2 11/10 | ## Theorie-Seminar (Brookhaven National laboratory) |

02. 05. 2014 at 13:00S2 11/10 | ## Theorie-SeminarHuey-Wen Lin (University of Washington) Quantum chromodynamics (QCD) is the theory describing the strong interactions of gluon and quarks in the Standard Model. It is responsible for nuclei and their interactions, with applications from femtometer to astrophysical scales. Unfortunately, many interesting aspects of the low-energy physics of QCD, especially in nuclear phenomenology, are yet to be explored with controllable systematics. In order to get reliable quantitative results in the nonperturbative region of QCD, a direct approach composing by the quark and gluon degrees of freedom is desired. |

02. 05. 2014 at 09:00S2 15/134 | ## Theorie-SeminarJens Braun (TU Darmstadt) The theory of the strong interaction describes the dynamics of the fundamental building blocks of nuclei, and the states of matter in the early stages of the universe. Relativistic heavy-ion collisions probe such |

28. 04. 2014 at 16:00S2 11/10 | ## Theorie-SeminarZoltan Fodor (University of Wuppertal) In this talk a short introduction to lattice QCD is presented and the importance of the physical limit (continuum extrapolation and physical quark masses) is emphasized. A few selected topics are discussed. The hadron spectrum and quark masses are determined. Techniques for many-nucleon sytems with sub-per-mil accuracies are presented. The transition temperature and the equation of state in the hot QCD plasma are calculated. |

23. 04. 2014 at 14:00S2 11/10 | ## Theorie-SeminarWitek Nazarewicz (University of Tennessee) The physics of Open Quantum Systems has attracted a lot of attention in many fields of physics. In atomic nuclei, the "openness" of the system manifests itself by the coupling to the many-body continuum representing various decay, scattering, and reaction channels. Due to the presence of particle thresholds, atomic nuclei form a network of correlated fermionic systems interconnected via reaction channels. |

16. 04. 2014 at 13:00S2 11/10 | ## Theorie-SeminarAleksi Vuorinen (University of Helsinki) I will discuss the role of perturbation theory in the description of strongly interacting matter either in or close to thermal equilibrium. Some examples of the quantities considered are the bulk thermodynamic and transport properties of hot quark-gluon plasma as well as the equation of state of cold and dense nuclear/quark matter. I will argue that a novel pairing of weak coupling techniques with other, nonperturbative approaches enables progress with problems that would otherwise be inaccessible by current first principles field theory tools. |

04. 04. 2014 at 12:00S2 11/10 | ## Lunch Club SeminarAnton Cyrol (TU Darmstadt) We report on the first Dyson-Schwinger calculation of the four-gluon vertex dressing function that contains all perturbatively leading one-loop diagrams. To diminish the impact of non-Bose-symmetric and hence unphysical parts, we symmetrize the four-gluon vertex Dyson-Schwinger equation (DSE). The propagators are dressed by the numerical results from Ref. [1] that agree well with lattice data. We take the ghost-gluon vertex as bare and dress the three-gluon vertex by the results obtained in Ref. [2]. By iterating the four-gluon vertex DSE, we find that the swordfish diagram is the dominant one. We compare our results to models used in previous Dyson-Schwinger calculations and determine the running coupling from the four-gluon vertex. Finally, an outlook for my master's thesis is given. |

13. 03. 2014 at 14:00S2 11/10 | ## Theorie-SeminarEric van Dalen (University of Tuebingen) In this seminar the results of theoretical investigations with realistic NN interactions are presented. The properties of infinite isospin asymmetric nuclear matter have been investigated in a relativistic Dirac-Brueckner-Hartree-Fock (DBHF) framework using the Bonn A potential. Results for the binding energy, the symmetry energy, the neutron-proton effective mass splitting, and the isovector nucleon optical potential are discussed. A problem is that the DBHF approach is too complex to be applied for other nuclear systems such as the neutron star crust and nuclei. However, these DBHF results can be applied to these systems within the framework of a density dependent relativistic mean field (DDRMF) theory. The predictions from this DDRMF model for the structure and properties of the neutron star crust and a few selected nuclei will be presented. Finally, an alternative to this DDRMF model, a low momentum interaction, will be discussed. |

11. 03. 2014 at 14:00S2 11/10 | ## Theorie-SeminarJohannes Kirscher () An effective field theory is a systematic description of a subset of the physical world of all observables. While those subsets may overlap, there is at least a trusted prescription of how to link their effective descriptions consistently. Although, effective field theories have been used in the realm of nuclei for decades, we still lack precise knowledge about the elements and boundaries of this peculiar subset, in particular, especially along the axis of increasing particle number. |

21. 02. 2014 at 14:00S2 11/10 | ## Theorie-SeminarRagnar Stroberg (Michigan State University / NSCL) A prominent theme in the study of the nuclear structure of exotic isotopes has been the disappearance of the shell closures found at stability and the appearance of new shell closures. The shell closure at N = 28 is of particular interest because it is the first shell closure that arises due to the strong spin-orbit splitting which is responsible all higher shell closures. N = 28 has been shown to disappear at large isospin, and this disappearance is particularly clear at 42Si (N = 28, Z = 14). This region is particularly difficult for shell model calculations with phenomenological interactions because they depend on cross-shell matrix elements which are poorly constrained by experimental data. Nonetheless, effective interactions have been developed which reproduce the collective observables around 42Si, while their microscopic predictions differ. In this talk, I will discuss the use of single-nucleon knockout reactions to investigate the disappearance of the N = 28 shell gap from a single-particle perspective. |

20. 02. 2014 at 14:00S2 11/10 | ## Theorie-SeminarDr. Enrico Vigezzi and Prof. Francisco Barranco (INFN Milan / Univ. of Sevilla) The interplay of collective and quasi particle degrees of freedom plays an important role in the study of the nuclear structure and reactions. |

04. 02. 2014 at 12:00S2 11/10 | ## Lunch Club SeminarGeorg Bergner () |

30. 01. 2014 at 14:00S2 11/10 | ## Theorie-SeminarMartin Hoferichter (University of Bern) The interpretation of experiments aiming at the direct detection of Dark Matter by measuring the recoil on a nuclear target in high-sensitivity detectors requires knowledge of the scalar couplings of the nucleon. |

23. 01. 2014 at 14:00S2 11/10 | ## Theorie-SeminarJonathan Engel (University of North Carolina) |

21. 01. 2014 at 12:00S2 11/10 | ## Lunch Club SeminarSam Jones (Keele University) New models, improved nuclear physics and hydrodynamic mixing uncertainties. |

10. 01. 2014 at 10:00S2 11/10 | ## Theorie-SeminarDr. Alessandro Lovato (ANL) I will report on an ab initio calculation of the 12-Carbon charge form factor and sum rules of electromagnetic and neutral-current response functions. The longitudinal elastic form factor and the electromagnetic sum rules are found to be in satisfactory agreement with available experimental data. The transverse electromagnetic and neutral current sum rules receive large contributions from the two-body currents. In the Electromagnetic case they are needed for a better agreement with experimental data; this fact may have implications for the anomaly observed in recent neutrino quasi-elastic charge-changing scattering data off 12-Carbon. |

10. 12. 2013 at 12:00S2 11/10 | ## Lunch Club SeminarPhilipp R. John (Dipartimento di Fisica e Astronomia, Universita di degli Studi Padova e Instituto Nazionale di Fisica Nuclear, Sezione di Padova, I-35131 Padova, Italy) |

05. 12. 2013 at 14:00S2 11/10 | ## Theorie-SeminarGabriele Cescutti () In the last years our group has found many chemical anomalies observed |

03. 12. 2013 at 12:00S2 11/10 | ## Lunch Club SeminarAnja Habersetzer (Frankfurt) |

14. 11. 2013 at 14:00S2 11/10 | ## Theorie-SeminarOleg Korobkin (Stockholm University) |

12. 11. 2013 at 12:00S2 11/10 | ## Lunch Club SeminarNoriyoshi Ishii (CCS, Tsukuba University) We will present our recent results on LS force(NN) and anti-symmetric LS force (hyperon interaction) from lattice QCD. We begin with a brief review of our strategy in constructing inter-baryon potentials and some related topics. The potentials are obtained from Nambu-Bethe-Salpeter (NBS) wave functions [HAL QCD method], which has been applied to many systems, such as NN, YN, YY, NNN, etc. These studies are restricted to local potentials (potentials which do not involve derivatives) in the parity-even sector. The restriction is due to source functions which these calculations employ, i.e., these calculations employ source functions with A1 representation of the cubic group such as the wall source and a smearing source. By using a momentum wall source with non-trivial cubic group transformation property, we study NN potentials in the parity-odd sector as well as the LS potentials. (LS potentials involve a single derivative) A strong attractive LS force with a weak repulsive central force in spin triplet P-wave channels lead to an attraction in the 3P2 channel, which is related to the P-wave neutron pairing in neutron stars. We extend this method to the hyperon sector, and consider a phenomenologically expected cancellation between the symmetric and the anti-symmetric LS potentials in the flavor SU(3) symmetric limit. |

06. 11. 2013 at 14:00S2 11/10 | ## Theorie-SeminarBarry Holstein (University of Massachusetts) |

31. 10. 2013 at 14:00S2 11/10 | ## Theorie-Seminar () The magneto-rotational mechanism represents an alternative explosion mechanism of core-collapse supernovae. The jet like explosion character associated with the magnetic mechanism may potentially explain the growing observational evidence that core-collapse supernovae are intrinsically aspherical. Moreover, it has been suggested that these events provide a promising site for the strong r-process. |

24. 10. 2013 at 14:00S2 11/10 | ## Theorie-SeminarDmitry Gridnev (FIAS) Nowadays in physics one finds numerous examples of few-body systems with large spatial extension. One could mention neutron halos in nuclear physics, Rydberg and Efimov states, negative ions in atomic and molecular physics. In all cases a large spatial extension of the many body wave function, which stretches beyond the classically allowed region, is a consequence of the fact that the energy of a bound state lies in close proximity to the dissociation threshold. A natural question arises, what would happen to a wave function of a system of N particles without clusters when a bound state approaches zero energy threshold. Relatively recently this question for three-body systems has been ultimately and rigorously resolved. It turns out that if none of the particle pairs have zero energy resonance then the system of three particles can possess a bound state at zero energy. Unlike negative energy bound states, which decay exponentially, a bound state with zero energy decays like an inverse power of a hyperradius, but still remains square integrable. The existence of a zero energy bound state sets limits on the size of two neutron halos, which are seen at the neutron drip line. If just one pair of particles has a zero energy resonance one gets a different situation: the ground state of three particles is no more square integrable at zero energy. This implies that a bound state, which approaches zero energy threshold totally spreads. Thereby, the wave function of three particles approaches a universal form, which does not depend on the details of the pair interaction. This is a first example of universality, which concerns wave functions rather than relations in the spectrum. Remarkably, the universal angular correlations match very well the dineutron peak that is seen in the wave functions of $^6$He and $^{11}$Li nuclei. If two or all three particle pairs have zero energy resonance, one arrives at the so-called Efimov effect. The obtained results, in particular, explain why the Efimov effect is only possible for three bosons, not more not less. |

23. 10. 2013 at 11:00S2 11/207 | ## Theorie-SeminarMichael Urban (IPN, Orsay) The superfluid phase transition in nuclear and neutron matter is studied within a Nozieres-Schmitt-Rink like approach. In symmetric matter at low density, a Bose-Einstein condensate (BEC) of deuterons is formed, while in the limit of high density the BCS limit is recovered. However, the crossover between the two limits lies inside the unstable region of the liquid-gas phase transition. It turns out that the presence of correlated pairs in the gas somewhat reduces the unstable region. In neutron matter, because of the large negative neutron-neutron scattering length, the BCS side of the crossover can be studied almost from the unitary limit to the BCS limit. In this calculation, an effective low-momentum interaction (V_low-k) is employed. The main result is that at low density, the superfluid critical temperature is substantially reduced compared to the BCS one. |

22. 10. 2013 at 12:00S2 11/10 | ## Lunch Club SeminarKirill Boguslavski () We study the non-equilibrium dynamics of longitudinally expanding systems using classical-statistical real-time lattice simulations. For non-abelian plasmas, different thermalization scenarios have been proposed to occur in ultrarelativistic heavy-ion collisions in the limit of weak couplings and large nuclei. Remarkably, we observe a turbulent attractor solution that distinguishes between these different scenarios. |

17. 10. 2013 at 14:00S2 11/10 | ## Theorie-SeminarCarlo Barbieri (University of Surrey) As ab-initio nuclear theory enter the mass range of A=40-100 particles, a great challenge is how to provide accurate predictions for the vast majority of open-shell (degenerate) isotopes. Here, the biggest challenges are to avoid the need for degenerate reference states and to include three-nucleon (and possibly many-nucleon) interactions that arise naturally in the nuclear Hamiltonian. |

15. 10. 2013 at 12:00S2 11/10 | ## Lunch Club SeminarBardiya Bahrampour (TU Darmstadt) |

19. 09. 2013 at 14:00S2 11/10 | ## Theorie-SeminarArianna Carbone (University of Barcelona) |

18. 09. 2013 at 14:00S2 11/10 | ## Theorie-Seminar (North Carolina State Univ.) |

17. 09. 2013 at 14:00S2 11/10 | ## Theorie-SeminarSanjay Reddy (INT/University of Washington) |

31. 07. 2013 at 14:00S2 11/10 | ## Theorie-SeminarTakaharu Otsuka (University of Tokyo) |

25. 07. 2013 at 14:00S2 11/10 | ## Theorie-SeminarDr. Susanne Kreim (CERN and MPIK Heidelberg) Experimentally, complementary observables are available to ameliorate our understanding of the nucleus, its mass being the most fundamental property. Together with the known mass of the individual constituents of the nucleus, the mass delivers the binding energy, which in turn reflects all underlying interactions of the nucleons. Precision measurements of masses can thus give insight into the faces of the nuclear force. |

18. 07. 2013 at 14:00S2 11/10 | ## Theorie-SeminarJames P. Vary (Iowa State University) |

17. 07. 2013 at 14:00S2 11/10 | ## Theorie-SeminarIan Cloet (Argonne National Laboratory) Quantum Chromodynamics (QCD) is the only known example in nature of a fundamental quantum field theory that is innately non-perturbative. Solving QCD will have profound implications for our understanding of the natural world, for example, it will explain how light quarks and massless gluons bind together to form the observed mesons and baryons and hence the origin of more than 98% of the visible mass in the universe. Given QCDs complexity, the best promise for progress is a strong interplay between experiment and theory. I will discuss several theoretical studies in continuum QCD that have been motivated by key experimental results that challenged our understand of nucleon and nuclear structure. For example, the proton GE/GM form factor ratio, EMC effect and NuTeV anomaly. A perspective will be given on what these experiments tell us about the non-perturbative structure of QCD and several predictions will be presented that should be tested in future experiments. |

16. 07. 2013 at 15:30S2 11/10 | ## Theorie-SeminarPaul Springer () |

15. 07. 2013 at 15:00S2 11/10 | ## Theorie-SeminarReinhard Alkofer () |

11. 07. 2013 at 14:00S2 11/10 | ## Theorie-SeminarCalvin W. Johnson (San Diego State University) You often hear about "fine-tuning" of parameters: some phenomena such as the abundances of heavy elements dependence sensitively on the exact strength of the interaction. What about the opposite? Are there phenomena which are exquisitely insensitive to the details of the interaction? Surprisingly, there are: to name just one of many, the ground state spins of even-even "nuclei" are dominated by J = 0 in shell-model simulations even when the interactions are completely random. The origin of this emergent behavior lies in surprising universality among many-body matrix elements, and can be found in a simple analytic model combining randomness and symmetry. |

03. 07. 2013 at 17:30S2 11/207 | ## Joint Nuclear Astrophysics SeminarCamilla J. Hansen (Landessternwarte, Heidelberg University) Stellar spectra carry a wealth of information, and depending on their resolution we can extract e.g. the stellar ages, chemical composition, radial velocities, as well as the stellar parameters. By observing a large sample of different stars with high-resolution spectrographs, we can investigate the chemical evolution, of all elements detectable, from lithium to uranium. Furthermore, knowing the complete abundance pattern of the star enables a comparison with model predictions, which in turn will provide information on the formation site and process of the detected elements. |

03. 07. 2013 at 16:30S2 11/10 | ## Joint Nuclear Astrophysics SeminarKerstin Sonnabend () There are about 35 proton-rich nuclei whose production cannot be explained by neutron capture processes. The synthesis of these so-called p nuclei is thought to be realized in different astrophysical scenarios which are usually referred to as sites of p-process nucleosynthesis. These scenarios will be briefly introduced including the different approaches to determine the nuclear physics needed for their modelling. As a highlight, the production of the lightest p nuclei via proton capture reactions in thermonuclear supernovae will be presented. Two recent publications [1,2] found a significant contribution to the production of the most abundant p nucleus 92-Mo by this mechanism. Experimental approaches for the determination of the required reaction rates will be explained and first results will be shown. |

03. 07. 2013 at 10:15S2 11/10 | ## CSC / Dense Matter SeminarDaniel Fernandez-Fraile (Frankfurt) |

20. 06. 2013 at 14:00S2 11/10 | ## Theorie-Seminar (Uni Basel) |

11. 06. 2013 at 12:00S2 11/207 | ## Lunch Club SeminarSixue Qin () |

14. 05. 2013 at 12:00S2 11/207 | ## Lunch Club SeminarKirill Boguslavski () Non-equilibrium fixed points and wave turbulence have been predicted for systems across different energy scales ranging from early-universe inflaton dynamics to experiments with ultracold atoms. Using classical-statistical lattice gauge theory simulations, the existence of a non-thermal fixed point is demonstrated for the space-time evolution of heavy-ion collisions in the limit of large nuclei at high energy. Most remarkably, the obtained scaling exponents can be explained by ordinary elastic scattering. We extend our discussion to the O(N) scalar field theory in a longitudinally expanding background to compare the scaling exponents and thus the underlying processes. |

07. 05. 2013 at 14:00S2 11/207 | ## Theorie-SeminarProf. Dr. Silas Beane (University of New Hampshire) I will discuss recent progress in calculating nuclear physics interactions and properties using lattice QCD. I will first focus on an area in which lattice QCD will soon be competitive with experiment; specifically, I will consider simple hypernuclear processes which are essential input into the nuclear equation of state relevant for a description of dense astrophysical objects. I will also discuss recent calculations of the spectrum of light nuclei and hypernuclei at the flavor SU(3) symmetric point. Finally, I will discuss very recent work which determines the nucleon-nucleon s-wave phase shifts at the SU(3) point. |

18. 04. 2013 at 14:00S2 11/10 | ## Theorie-SeminarFilippo Galeazzi (U. Valencia) |

12. 03. 2013 at 12:30S2 11/10 | ## Lunch Club SeminarAndreas Windisch (KFU Graz) We use Graphics Processing Units (GPUs) to calculate the analytic structure of QFT Green's functions. We extend a technique developed for the evaluation of the analytic structure of scalar glueball operators at the Born level such that it is suitable for a fully non-perturbative treatment in the Dyson-Schwinger approach. In particular we discuss how this method can be used to obtain the analytic structure of the Landau gauge quark propagator. |

12. 03. 2013 at 12:00S2 11/10 | ## Lunch Club SeminarMarkus Hopfer (KFU Graz) The coupled system of the quark-gluon vertex and quark propagator Dyson-Schwinger equations (DSEs) is investigated within Landau gauge QCD. The aim is to get a deeper insight into the mechanisms of quark confinement and dynamical chiral symmetry breaking and into a possible relation between these two phenomena. To this end an earlier study is extended by improving systematically on the truncations imposed on the quark-gluon vertex DSE. A clear infrared enhancement for all tensor structures of the quark-gluon vertex is obtained. |

19. 02. 2013 at 12:00S2 11/10 | ## Lunch Club SeminarBardiya Bahrampour (TU Darmstadt) Master thesis proposal presentation. |

07. 02. 2013 at 15:00S2 11/207 | ## Theorie-SeminarTilman Enss () Can a real fluid flow without friction? Following the conjecture that quantum mechanics imposes a universal lower bound on the shear viscosity, this question is being studied intensively in several fields of physics ranging from quark-gluon plasmas to ultracold atomic gases. I will discuss the origin of this bound and present results for the frequency dependent shear viscosity of strongly interacting Fermi gases, which exhibits a universal high-frequency tail. Motivated by a recent experiment with spin-polarized clouds of atoms, I present recent calculations and discuss the prospect of a quantum bound for spin transport. |

22. 01. 2013 at 12:00S2 11/207 | ## Lunch Club SeminarMeng-Ru Wu (TU Darmstadt) |

08. 01. 2013 at 13:00S2 11/207 | ## Theorie-SeminarHeiko Hergert (The Ohio State University) |

13. 12. 2012 at 14:00S2 11/207 | ## Theorie-SeminarJanos Polonyi (Strasbourg) It is shown in the framework of a simple classical, harmonic model that irreversibility, generated by the environment is a spontaneous breakdown of the time reversal invariance which is driven by the environment initial conditions. The Closed Time Path method is outlined in classical mechanics as a systematic way to handle initial condition problems and dissipative forces by an action principle. The equivalence of the classical and quantum time arrows, generated by the environment is pointed out, as well. |

11. 12. 2012 at 12:00S2 11/207 | ## Lunch Club SeminarAlexander Stoffers (Stony Brook) We briefly review the approach to dipole-dipole scattering |

04. 12. 2012 at 15:00S2 11/207 | ## No Lunch Club SeminarPhilipp Scior (TU Darmstadt) |

27. 11. 2012 at 12:00S2 11/207 | ## Lunch Club SeminarIssaku Kanamori () Although supersymmetry is broken with lattice regularization, a BRST-like part of the supersymmetry can be exactly realized on lattice in some systems. In low dimensional cases, this symmetry (Q-symmetry) is strong enough to guarantee the restoration of full supersymmetry in the continuum limit. I will present some results from 2-dimensional super Yang-Mills from lattice simulations with such symmetry. Another advantage of exact Q-symmetry is that it allows to define the Witten index at the lattice level, which is a useful index to discuss spontaneous supersymmetry breaking. I will also present how to measure the Witten index from lattice simulations. |

22. 11. 2012 at 17:00S2 07/167 | ## Joint Nuclear Astrophysics SeminarKlaus Blaum (Uni Heidelberg) Among all nuclear ground-state properties, atomic masses are highly specific for each particular combination of N and Z and the data obtained apply to a variety of physics topics. One of the most crucial questions to be addressed in mass spectrometry of unstable radionuclides is the one of understanding the processes of element formation in the Universe. To this end, accurate atomic mass values of a large number of exotic nuclei participating in nucleosynthesis are among the key input data in large-scale reaction network calculations. |

22. 11. 2012 at 16:00S2 07/167 | ## Joint Nuclear Astrophysics SeminarAchim Schwenk (TU Darmstadt) For more information see https://indico.gsi.de/conferenceDisplay.py?confId=1973 |

20. 11. 2012 at 12:00S2 11/207 | ## Lunch Club Seminar (Uni Basel) |

19. 11. 2012 at 14:00S2 11/10 | ## Theorie-SeminarFrederic Nowacki (Institut Pluridisciplinaire Hubert Curien, Strasbourg, France) In this seminar, we will present some of the last developments in |

19. 11. 2012 at 10:00S2 11/10 | ## CSC / Dense Matter SeminarWolfgang Unger (Frankfurt) |

15. 11. 2012 at 12:00S2 11/10 | ## Theorie-Seminar (Brookhaven National Laboratory) |

08. 11. 2012 at 14:00S2 11/207 | ## Theorie-SeminarVladimir Skokov (Brookhaven National Laboratory) |

06. 11. 2012 at 12:00S2 11/207 | ## Lunch Club SeminarMichael Urban (IPN, Orsay) The pygmy dipole resonance in neutron-rich nuclei is studied within the framework of the Vlasov equation which is solved numerically. The interaction used in the Thomas-Fermi ground state and in the Vlasov equation is derived from an energy functional which correctly describes the equation of state of nuclear matter and neutron matter. It is found that the pygmy resonance appears in the electric dipole response of all nuclei with strong neutron excess, the energies and transition probabilities being in reasonable agreement with experimental results. Since the Vlasov equation does not account for any shell effects, this indicates that the existence of the pygmy resonance is a generic phenomenon and does not rely on the specific shell structure. Besides the electric dipole response, the isoscalar toroidal response is calculated. The transition densities and velocity fields are discussed. A comparison of the peak positions and velocity fields suggests that the pygmy resonance can be identified with one of the low-lying modes excited by the isoscalar toroidal operator. |

05. 11. 2012 at 14:00S2 11/207 | ## Theorie-SeminarAndrea Idini () Within the framework of nuclear field theory (NFT), the spectrum of atomic nuclei is described in terms of collective and quasiparticle degrees of freedom, that is, of elementary modes of nuclear excitation and of their interweaving. These modes are directly related to experiment. In fact, the associated transition densities and spectroscopic amplitudes are the basic ingredients entering in the calculations of inelastic, one- and two-particle transfer absolute differential cross sections. The workings of the Dyson equation, which propagates NFT medium polarization processes to all orders of perturbation, and which results in the dressing of quasiparticles and in the renormalization of the pairing interaction, will be discussed. The formalism will be applied to the superfluid nucleus 120Sn and to the exotic doubly closed shell nucleus 132Sn. |

01. 11. 2012 at 14:00S2 11/207 | ## Theorie-SeminarMicaela Oertel (LUTH, Observatoire de Paris, Meudon) The phase diagram of a system constituted of neutrons and Lambda-hyperons in thermal equilibrium is evaluated in the mean-field approximation. It is shown that this simple system exhibits a complex phase diagram with first and second order phase transitions. Due to the generic presence of attractive and repulsive couplings, the existence of phase transitions involving strangeness appears independent of the specific interaction model. In addition I will discuss under which conditions a phase transition towards strange matter at high density exists, which is expected to persist even within a complete treatment including all the different strange and non- strange baryon states. I will show in particular that upon adding a charge degree of freedom, i.e. protons and electrons, the strangeness-driven phase transition stays almost unaffected contrary to the subsaturation liquid-gas transition. Consequences for stellar matter under the condition of strangeness equilibrium will be briefly discussed. |

30. 10. 2012 at 16:00S2 11/10 | ## Theorie-SeminarAleksi Kurkela (McGill University) |

30. 10. 2012 at 12:00S2 11/207 | ## Theorie-SeminarJohannes Hofmann (Cambridge U) The behaviour of cold Fermi gases is largely independent of the microscopic details of the interatomic interaction and can be described by a small set of parameters. It is, nevertheless, still a challenging task to calculate observables exactly, especially if the system is strongly interacting. However, if the observable depends on a large external scale, the functional dependence on that scale can be determined in closed analytical form. One method to derive such 'universal relations' is via the operator product expansion (OPE). I would like to introduce the application of this method to cold Fermi gases and to present results for the dynamic structure factor and the shear viscosity. I shall also give an overview of recent work that applies the OPE to fermions interacting with a long-range Coulomb interaction. I will conclude the talk by discussing a quantum anomaly in two-dimensional Fermi gases. |

26. 10. 2012 at 13:00S2 11/10 | ## Theorie-SeminarDirk Rischke () |

25. 10. 2012 at 13:00S2 11/10 | ## Theorie-SeminarGert Aarts (Swansea University) |

24. 10. 2012 at 16:00S2 11/10 | ## Theorie-SeminarHarvey Meyer () |

24. 10. 2012 at 13:00S2 11/10 | ## Theorie-SeminarEvgeny Epelbaum () |

23. 10. 2012 at 16:00S2 11/10 | ## Theorie-SeminarJan Pawlowski () |

23. 10. 2012 at 13:00S2 11/10 | ## Theorie-SeminarAleksi Vuorinen () |

19. 10. 2012 at 14:30S2 11/207 | ## Theorie-SeminarMichael Ilgenfritz (JINR, Dubna) I motivate the current interest in the cross-effects of QCD and Abelian Electrodynamics, in particular from the point of view of Heavy Ion Collisions. Since long the effect of an external magnetic field on chiral symmetry breaking (magnetic catalysis) has been considered in various models. More recently, the effect on the thermal phase transition of QCD and its deconfining and chiral symmetry restoration aspects is in the focus of effective models and of ab initio lattice simulations. |

17. 10. 2012 at 11:00S2 14/024 | ## Theory ColloquiumDonald Lynden-Bell (University of Cambridge) |

16. 10. 2012 at 12:00S2 11/207 | ## Lunch Club SeminarSoeren Schlichting () |

17. 09. 2012 at 14:00S2 11/207 | ## Theorie-SeminarEvan O'Connor (CITA) |

07. 08. 2012 at 12:00S2 11/207 | ## Lunch Club SeminarFrank Saueressig () |

02. 08. 2012 at 14:00S2 11/207 | ## Theorie-SeminarReinhard Alkofer () Electron-positron pair production for short laser pulses with multiple time-scale sub-structures is considered in the nonperturbative regime (Schwinger pair production). After a short discussion of the underlying mechanism the non-equilibrium quantum kinetic approach is introduced. Results for the momentum spectra of the created electron-positron pairs are presented. These may lead to new probes of light pulses at extremely short time scales. Considering suitably combined time-scales and field strengths can lead to a significant enhancement in the production rates (dynamically assisted Schwinger effect) and interferences in the obtained spectra. Recent attempts to apply optimal control theory for pulse shaping are reported. Last but not least, some results on pair creation in space- and time-dependent fields are presented. |

31. 07. 2012 at 12:00S2 11/207 | ## Lunch Club SeminarJan Stockemer () |

19. 07. 2012 at 14:00S2 11/10 | ## Theorie-SeminarFriedel Thielemann () We give a short review on necessary conditions in order to achieve a sufficient neutron/seed ratio for an r-process to occur, what are the candidate astrophysical sites to fulfill such conditions (supernovae, magnetar-forming supernovae, quark (super-)novae, neutron star mergers,...), what is their role in the chemical evolution of galaxies, and did there existed a chance to produce superheavy elements in nature? |

05. 07. 2012 at 14:00S2 11/10 | ## Theorie-SeminarRaphael Hirschi (Keele University) After a brief introduction to the evolution of massive stars, I will describe the effects of rotation and metallicity on their evolution. I will then present recent results on the impact of rotation on the weak s process at low metallicities. I will end the seminar with a discussion of key nuclear physics uncertainties relevant for massive star evolution and nucleosynthesis (neutron poisons, electron captures and C12-C12). |

28. 06. 2012 at 14:00S2 11/10 | ## Theorie-Seminar () The collapse and the explosion of massive stars at the end of their |

19. 06. 2012 at 12:00S2 11/207 | ## Lunch Club SeminarFrank Saueressig () |

14. 06. 2012 at 14:00S2 11/207 | ## Theorie-SeminarAlbino Perego (Basel) |

13. 06. 2012 at 11:00S2 11/10 | ## Theorie-SeminarMartin Savage (University of Washington) A century of coherent experimental and theoretical investigations have uncovered the laws of nature that underly nuclear physics. Quantum Chromodynamics (QCD) and Quantum Electrodynamics (QED), both quantum field theories with a small number of precisely constrained input parameters, dominate the dynamics of the quarks and gluons - the underlying building blocks of protons, neutrons, and nuclei. While the analytic techniques of quantum field theory have played a key role in understanding the dynamics of matter in high energy processes, they encounter difficulties when applied to low-energy nuclear structure and reactions, and dense systems. |

12. 06. 2012 at 12:00S2 11/10 | ## Lunch Club SeminarMarcella Ugliano (Max Planck Institute for Astrophysics) |

05. 06. 2012 at 12:00S2 11/207 | ## Lunch Club SeminarFrank Saueressig () |

22. 05. 2012 at 12:00S2 11/10 | ## Theorie-SeminarDean Lee (NC State University) Effective field theory provides a systematic approach to interacting quantum systems at low energies and densities. Lattice effective field theory combines this approach with non- perturbative lattice methods. I discuss recent applications of lattice effective field theory to the physics of cold atomic superfluids, neutron matter, and nuclei. I also discuss new developments and ideas in the field. |

21. 05. 2012 at 14:00S2 11/10 | ## Theorie-SeminarStephan Rosswog (Jacobs University Bremen) |

18. 05. 2012 at 11:00S2 11/10 | ## Theorie-SeminarWitold Nazarewicz (University of Tennessee/ORNL) Nuclei communicate with us through a great variety of observables. Some are easy to |

15. 05. 2012 at 12:00S2 11/207 | ## Lunch Club SeminarMatthias Hempel (University of Basel) We present new equations of state (EOS) which are available for use in astrophysical simulations. Their characteristic properties are confronted with experimental and observational constraints, with focus on recent results for the symmetry energy. The role of the EOS in core-collapse supernovae is investigated by use of spherical simulations with detailed neutrino transport. First we briefly discuss the distributions of heavy nuclei during collapse and the abundant appearance of light nuclei like deuterons and tritons in the shock heated matter. Then we analyze the role of the high-density EOS in the later post-bounce phase. In addition to the properties of the cold nuclear matter EOS, we find that complementary temperature effects can be crucial for the dynamics. |

24. 04. 2012 at 12:00S2 11/207 | ## Lunch Club SeminarSandeep Chatterjee (Indian Institute of Science, Bangalore, India ) We consider the (2 + 1) flavor Polyakov Quark Meson Model (PQM) and study the effect of including fermion vacuum fluctuations on the thermodynamics and phase diagram. The variation of the thermodynamic quantities across the phase transition region becomes smoother. This results |

17. 04. 2012 at 12:00S2 11/207 | ## Lunch Club SeminarLeonard Fister () We study the temperature dependence of correlators in Yang-Mills theory. For this purpose we utilise a purely thermal renormalisation group flow equation, and obtain the full thermal propagators. Interestingly, the electric screening mass is sensitive to the confinement-deconfinement phase transition. We also compute thermodynamic quantities such as the pressure. |

13. 04. 2012 at 14:30S2 14/401 | ## otherHaris Djapo (Akdeniz University, Antalya) |

28. 02. 2012 at 12:00S2 11/207 | ## Lunch Club SeminarKirill Boguslavski (TU Darmstadt) |

16. 02. 2012 at 14:00S2 11/207 | ## Theorie-SeminarProf. Dr. Evgeny Epelbaum () Chiral effective field theory provides a systematic framework toow-energy dynamics of few-nucleon systems and light nuclei based on (the symmetries of) QCD. Using a discretized version of this approach by treating pions and nucleons as point-like particles on an Euclidean space-time lattice allows to evaluate the path integral by Monte Carlo sampling and to access the properties of heavier systems. I describe the foundations of this method and consider the applications to the spectra of light nuclei. |

14. 02. 2012 at 12:00S2 11/207 | ## Lunch Club SeminarShun Furusawa (Waseda University, Japan) We calculate a new equation of state for baryons at sub-nuclear densities for the use in core-collapse simulations of massive stars. The formulation is the nuclear statistical equilibrium description and the liquid drop approximation of nuclei. The model free energy to minimize is calculated by relativistic mean field theory for nucleons and the mass formula for nuclei with atomic number up to ~1000. We have also taken into account the pasta phase. We find that the free energy and other thermodynamical quantities are not very different from those given in the standard EOSs that adopt the single nucleus approximation. On the other hand, the average mass is systematically different, which may have an important ramification to the rates of electron captures and coherent neutrino scatterings on nuclei in supernova cores. |

09. 02. 2012 at 14:00S2 11/207 | ## Theorie-SeminarDr. Alexander E. Dorokhov (JINR, Dubna) A short review of some recent experimental and theoretical studies of the light pseudoscalar mesons is presented. It concerns the problem of the muon g-2 and mesonic contributions to it, the rare mesonic decays to lepton pairs, the transition form factors at large momentum transfer, and a generalized quark transversity distribution of the pion. |

07. 02. 2012 at 12:00S2 11/207 | ## Lunch Club SeminarNaoki Yamamoto (INT Seattle) We discuss the phase diagrams of QCD and QCD-like theories from the viewpoints of the large-Nc universality and the quark-hadron continuity. First we show that the whole or the part of the phase diagrams are universal between QCD and QCD-like theories in the limit of large number of colors N_c. From our universality and QCD inequalities, we derive some rigorous results on the chiral phase transition at high temperature. Second we argue that the continuity from hadronic matter to quark matter should universally appear in flavor-symmetric QCD and QCD-like theories at low temperature and high density. We also discuss possible implications of our results. |

02. 02. 2012 at 14:00S2 11/207 | ## Theorie-SeminarProf. Dr. Wolfram Weise () |

31. 01. 2012 at 12:00S2 11/207 | ## Lunch Club SeminarKirill Boguslavski (TU Darmstadt) |

26. 01. 2012 at 14:00S2 11/207 | ## Theorie-SeminarProf. Andreas Wipf () We review recent progress on the G2-Higgsmodel and G2-QCD with dynamical fermions. In contrast to real QCD this Gauge Theory has no sign problem and can be investigated at finite baryon density. We review results on the Phases of the Higgsmodel and discuss preliminary results for the model with dynamical fermions at finite temperature and finite density. |

12. 01. 2012 at 14:00S2 11/207 | ## Theorie-SeminarProf. Dr. Michael Thies () Four-fermion theories in 1+1 dimensions of Gross-Neveu (discrete chiral symmetry) or Nambu--Jona-Lasinio (continuous chiral symmetry) type in the limit of a large number of flavors can be solved exactly. Nevertheless, they capture a rich variety of phenomena of interest to strong interaction physics. We review what has been learned about the phase diagrams of such models during the last decade. In the case of discrete chiral symmetry, the models can also be applied to conjugate polymers in condensed matter physics. In the case of continuous chiral symmetry, universal features emerge which are relevant for gauge theories as well, independently of whether fermions are confined or not. |

15. 12. 2011 at 14:00S2 11/207 | ## Theorie-SeminarProf. Dr. Owe Philipsen () |

06. 12. 2011 at 12:00S2 11/207 | ## Lunch Club SeminarAlexander Semke (TU Darmstadt/GSI) We perform a chiral extrapolation of the baryon octet and decuplet masses in a relativistic formulation of chiral perturbation theory. A partial summation is assumed as implied by the use of physical baryon and meson masses in the one-loop diagrams. Upon a chiral expansion our results are consistent with strict chiral perturbation theory at the next-to-next-to-next-to-leading order. All counter terms are correlated by a large-Nc operator analysis. Our results are confronted with recent results of unquenched three flavor lattice simulations. We adjust the parameter set to the pion-mass dependence of the nucleon and omega masses as computed by the BMW group and predict the pion-mass dependence of the remaining baryon octet and decuplet states. The current lattice simulations can be described accurately and smoothly up to pion masses of about 600 MeV. In particular we recover the recent results of HSC without any further adjustments. |

29. 11. 2011 at 12:00S2 11/207 | ## Lunch Club SeminarChristian Schmidt () We presents results on the chiral and deconfinement properties of the QCD transition at finite temperature. Calculations are performed using the p4, asqtad and HISQ/tree actions with 2 + 1 favors on lattices with temporal extent N = 6, 8 and 12 to understand and control discretization errors and to reliably extrapolate estimates obtained at finite lattice spacings to the continuum limit. |

10. 11. 2011 at 14:00S2 11/207 | ## Theorie-SeminarMarkus Huber (TU Darmstadt) A characteristic feature of the strong interaction is the absence of free quarks and gluons from the particle spectrum. To explain this phenomenon, called confinement, many scenarios have been invoked. However, they are not mutually exclusive and it even turned out that some of them are intimately connected. I present results on two such scenarios: the dual superconductor picture of confinement and the Gribov-Zwanziger scenario. In the former chromomagnetic monopoles are supposed to confine quarks, whereas in the latter the so-called Gribov horizon plays an important role. Although these two pictures are based on quite different motivations, they are related to each other. |

01. 11. 2011 at 12:00S2 11/207 | ## Lunch Club SeminarHans-Peter Pavel (TU Darmstadt and JINR Dubna) For the complete description of the physical properties of QCD, such as color confinement, chiral symmetry breaking, the spectra and strong interactions of hadrons, and the formation of condensates and flux-tubes, it might be advantageous to first reformulate QCD in terms of gauge invariant dynamical variables, before applying any approximation schemes. Using a canonical transformation of the dynamical quark and gluon variables, which Abelianises the non-Abelian Gauss-law constraints, such a reformulation can be achieved for 2-color QCD and is expected to be generalisable to the case of real QCD. The resulting unconstrained QCD-Hamiltonian admits a systematic expansion in the number of spatial derivatives. Introducing an infinite lattice with box length a and coarse graining the local gauge invariant fields, a systematic strong coupling expansion of the Hamiltonian in lambda= g^(-2/3) can be obtained, with the free part being the sum of Hamiltonians of Dirac-Yang-Mills quantum mechanics of constant fields for each box, and interaction terms of higher and higher number of spatial derivatives connecting different boxes. The corresponding deviation from the free glueball/hadron spectrum, obtained earlier for the case of Dirac-Yang-Mills quantum mechanics of spatially constant fields, is calculated using perturbation theory in lambda. As a first step, the interacting glueball vacuum and the energy spectrum of the interacting spin-0 glueball are obtained to order lambda^2. Its relation to the renormalisation of the coupling constant in the IR is discussed, indicating the absence of infrared fixed points. |

25. 10. 2011 at 12:00S2 11/207 | ## Lunch Club SeminarMicaela Oertel (CNRS/Observatoire de Paris) It has been known for a long time that within the different structures inside a neutron star we can find superfluid and superconducting ones. The first observational indications were the glitches, and more recently observations of the surface thermal emission have been discussed in this context. The latter |

24. 10. 2011 at 13:00S2 11/207 | ## Theorie-PalaverHans-Peter Pavel (TU Darmstadt and JINR Dubna) As an illustrative example the simplest case of a spin-0 glueball spectrum of SU(2) Yang-Mills quantum mechanics is calculated with high precision, using the analytical solutions of the corresponding 3-dim harmonic oscillator Schroedinger equation (a Calegero-type model) as appropriate basis states. |

17. 10. 2011 at 13:00S2 11/207 | ## Theorie-PalaverHans-Peter Pavel (TU Darmstadt and JINR Dubna) An introduction to the Hamiltonian formulation of gauge theories |

04. 10. 2011 at 12:00S2 11/207 | ## Lunch Club SeminarMichael Ilgenfritz (JINR, Dubna) The infrared structure of SU(2) Yang-Mills theory is studied by means of lattice gauge simulations using a new constrained cooling technique. This method reduces the action while all Polyakov lines on the lattice remain unchanged. In contrast to unconstrained cooling, quark confinement is still intact. A study of the Hessian of the Yang-Mills action shows that low action (semi-) classical configurations can be achieved, with a characteristic splitting between collective modes and higher momentum modes. Besides confinement, the semiclassical configurations also support the topological susceptibility and generate spontaneous breakdown of chiral symmetry. We show that they possess a cluster structure of locally mainly (anti-)selfdual objects. By contrast to an instanton or a meron medium, the topological charge of individual clusters is smoothly distributed. |

27. 09. 2011 at 12:00S2 11/207 | ## Lunch Club SeminarKai Schwenzer (Washington University, St Louis) In cold compact stars matter is expected to be superfluid and transport processes are significantly suppressed. Yet, we show that weak reactions become strongly enhanced and approach their ungapped level when the star undergoes density oscillations of sufficiently large amplitude. We present results for the neutrino emissivity and the bulk viscosity due to weak Urca processes in hadronic, hyperonic and quark matter and discuss different superfluid and superconducting pairing patterns. |

28. 07. 2011 at 14:00S2 11/207 | ## Theorie-SeminarJeff Greensite (San Francisco State University) Knowledge of the ground state wavefunctional of Yang-Mills theory ought to provide us with some insight into the infrared properties of the theory, confinement in particular. A number of proposals for this wavefunctional have been advanced in recent years, particularly in 2+1 dimensions. I will briefly review these proposals, and then describe the results of some recent numerical tests. I will also mention some new results which suggest that color electric flux tubes may survive at a range of temperatures above the deconfinement transition. |

26. 07. 2011 at 12:00S2 11/207 | ## Lunch Club SeminarLukas Janssen () 3d relativistic fermion system have fascinating applications to condensed-matter systems: In particular, QED3 and the 3d Thirring model are actively discussed, e.g., as effective theories describing different regions of the cuprate phase diagram and the electronic properties of graphene. Nonetheless, these theories are likewise intrinsically interesting: most notably, it is expected that chiral symmetry breaking is prohibited once the number of fermion flavors is larger than a critical value. In this talk I review the 3d Thirring model and its symmetries. With the help of the functional renormalization group I discuss the UV structure and possible condensation channels. I then reformulate the model in a partially bosonized language which is suitable for the investigation of dynamical mass generation. |

25. 07. 2011 at 14:30S2 11/207 | ## CSC Seminar (TU Darmstadt) |

22. 07. 2011 at 11:00S2 11/207 | ## Theorie-SeminarProf. James Vary (Iowa State University) The vision of solving the nuclear many-body problem with fundamental interactions tied to QCD via Chiral perturbation theory appears to approach reality. The goals are to preserve the predictive power of the underlying theory, to test fundamental symmetries with the nucleus as laboratory and to develop new understandings of the full range of complex nuclear phenomena. Advances in theoretical frameworks (renormalization and many-body methods) as well as in computational resources (new algorithms and leadership-class parallel computers) signal a new generation of theory simulations that will yield valuable insights into origins of nuclear shell structure, collective phenomena and complex reaction dynamics. I will outline some recent achievements and present ambitious consensus plans along with their challenges for a coming decade of research that will strengthen the links between nuclear theory and nuclear experiment, between nuclear physics and astrophysics, and between nuclear physics and nuclear energy applications. |

06. 07. 2011 at 13:00S2 11/207 | ## Theorie-PalaverDr Jean-Sebastien Gagnon (TU Darmstadt) In this Palaver I present a brief (non exhaustive) review of the dark energy problem. Starting from observational evidences for an accelerated universal expansion, I go on with the simplest solution to this problem (i.e. adding a cosmological constant to Einstein's equations) and show its ``unnaturalness''. If time permits, I will present some other ideas/models that have been proposed to explain this phenomenon (e.g. quintessence, braneworlds, voids). |

05. 07. 2011 at 12:00S2 11/207 | ## Lunch Club Seminar () |

29. 06. 2011 at 13:00S2 11/207 | ## Theorie-Seminar (TRIUMF, Canada) |

28. 06. 2011 at 12:00S2 11/207 | ## Lunch Club SeminarDr. Saori Pastore (Argonne National Laboratory) We discuss the derivation of the two-nucleon electromagnetic charge and current operators carried out in a chiral effective field theory (EFT) with pions and nucleons as explicit degrees of freedom. We include corrections up to order e Q -- where Q denotes the low-momentum scale and e is the electric charge. A review of the results obtained within this framework for a number of electromagnetic observables induced by the magnetic dipole operator -- including the n-d and n-3He radiative captures at thermal neutron energies -- is presented. |

21. 06. 2011 at 12:00S2 11/207 | ## Lunch Club SeminarHiroaki Kohyama (Chung Yuan Christian University, Taiwan) The UA(1) symmetry is broken due to the quantum effects. This plays a crucial role for low energy physics. The most important manifestation is the large mass of the eta prime meson which is comparable to the mass of the proton. It is expected that the UA(1) symmetry is restored at intermediate densities at which new states of quark matter such as color superconducting phases become dominant. In this talk, I consider the Nambu Jona-Lasinio model with UA(1) symmetry restoration at high density, and study the possible effect on meson properties and the QCD phase diagram. |

20. 06. 2011 at 13:00S2 11/207 | ## Theorie-PalaverDaniel Nowakowski (TU Darmstadt) In this talk I give a short introduction about the model of complex action by M. Ninomiya and H.B. Nielsen. Especially I focus on possible effects on the running of the Large Hadron Collider. Also an experiment, which would allow to test the fate of LHC with a card game, will be presented. Possible effects of the complex action model would be, that the Higgs suppresses its production by backward causation, e.g. in collider experiments. Therefore the appearance of many Higgs-particles in certain experiments would possess strong influence of the correctness of this theory. It is argued, that the accident of the LHC shortly after start was such a signal of suppression and that the cancelation of the Superconducting Super-Collider (SSC) was due to backward causation. In my palaver I will review critically the statements of Nielsen et al. for this model, point out further implications of complex actions and try to estimate, which future collider experiment is "allowed by the Higgs", if the model is true. If there is some time left, I wish to point out how the complex action model is related to EPS-Bell's Theorem problem. |

16. 06. 2011 at 10:00S2 11/207 | ## CSC seminarHarmen Warringa (Frankfurt) A two-component Fermi gas with attractive s-wave interactions forms a superfluid at low temperatures. When this gas is confined in a rotating trap, fermions can unpair at the edges of the gas and vortices can arise beyond certain critical rotation frequencies, as has been observed experimentally. I will discuss the computation of the critical rotation frequencies and present the phase diagram in the plane of scattering length and rotation frequency for different total number of particles. |

14. 06. 2011 at 12:00S2 11/207 | ## Lunch Club SeminarBardiya Bahrampour |

07. 06. 2011 at 12:00S2 11/207 | ## Lunch Club SeminarKurt Langfeld (University of Plymouth) The empty vacuum of SU(N) Yang-Mills theories is reviewed. The "flat directions" of gauge inequivalent vacuum states collapse to a discrete Z(N) symmetry due to quantum fluctuations. The importance of centre-sector tunnelling for confinement is explained. The Z(N) centre symmetry is lifted by including dynamical matter such as quarks. It is shown that centre sector transitions still occur in the low temperature phase. The impact of these transitions in QCD and QCD-like theories is revealed: a new state of confined matter rises at low temperatures and intermediate values of the chemical potential when Fermi-Einstein condensation takes place. This new mechanism is explained in some detail. |

31. 05. 2011 at 12:00S2 11/207 | ## Lunch Club SeminarV. Sreekanth (Physical Research Laboratory Ahmedabad, India) We investigate the thermal dilepton production-rates using one dimensional |

26. 05. 2011 at 14:00S2 11/207 | ## Theorie-SeminarProf. Simon Hands (Swansea University, Wales) After reviewing the QCD phase diagram and the problems in studying dense baryonic matter using orthodox lattice gauge theory methods, I present results of simulations of a QCD-like theory with gauge group SU(2) at non-zero quark chemical potential. Its behaviour as mu is increased is rich - there is evidence for three distinct regimes: first a Bose-Einstein condensate of tightly-bound but weakly-interacting diquarks; next a regime where the scaling of thermodynamic observables is consistent with a Fermi surface disrupted by a BCS instability;finally a deconfined phase. The deconfinement transition is distinct from the BEC/BCS crossover, hinting at quarkyonic behaviour. |

23. 05. 2011 at 13:00S2 14/401 | ## Theorie-Palaver (TU Darmstadt) In my talk, I will present some general ideas linking quantum and classical correlation. I will briefly talk about quantum entanglement and what seperates local theories as a class from QM. Also, i wish to point out experimental problems with detection efficiency and i will present a very easy model that abuses non-perfect detectors to reproduce quantum mechanical expectation values exactly while beeing local with the help of hidden variables. |

17. 05. 2011 at 12:00S2 11/207 | ## Lunch Club SeminarTomas Brauner () |

09. 05. 2011 at 13:00S2 11/207 | ## Theorie-PalaverNico Formanek (TU Darmstadt) I will talk about the basic concepts in quantum logic (e.g. some lattice theory) and how they relate to the algebraic concept of Hilbert spaces which are normally taught in physics. From a more philosophical point of view I hope to shed some light on how quantum logic might or might not illuminate some problems (hidden variables and the likes) which "haunt" the interpretations of quantum mechanics. |

03. 05. 2011 at 12:30S2 11/207 | ## Lunch Club SeminarFlorian Hebenstreit () Non-perturbative electron-positron pair creation in electric fields (Schwinger effect) has been a long-standing but still unobserved prediction of QED. Due to the advent of a new generation of high-intensity laser systems such as the European XFEL or the Extreme Light Infrastructure (ELI) it might, however, become possible to observe this effect within the next decades. Previous investigations led to a good understanding of the general mechanisms behind the pair creation process, however, realistic electric fields as they might be present in upcoming experiments have not been fully considered yet. |

15. 04. 2011 at 15:00S2 15/134 | ## Theorie-SeminarPD Dr. Antonio Vairo () Non-relativistic bound states are characterized by a hierarchy of energy scales that makes them well suited for an effective field theory treatment. I first illustrate this on the example of the hydrogen atom, for which I calculate the Lamb shift. Then I extend the formalism to the study of a quarkonium in a thermal bath. Quarkonium has been considered since long an ideal probe of the new state of matter, which is formed in high-energy heavy-ion experiments. The effect of the medium on the quarkonium spectrum and on its decay width is highlighted. The melting temperature of the bottomonium ground state is calculated. |

15. 04. 2011 at 14:00S2 15/134 | ## Theorie-SeminarDr. Brian Tiburzi (Massachusetts Institute of Technology) At scales a few billion times smaller than microscopic, the properties of protons and neutrons arise from interactions between quarks and gluons. While these QCD degrees of freedom have been identified for well over a quarter century, quantitative predictions from QCD at low energies have remained elusive until quite recently. I will review difficulties inherent in treating strong interactions, and describe progress being made at predicting properties of QCD. The response of QCD to external fields, moreover, will be argued to provide a new window to the structure of protons and neutrons, and the study of QCD under extreme conditions. |

15. 04. 2011 at 13:00S2 15/134 | ## Theorie-SeminarProf. Dr. Harvey Meyer () In the context of Quantum Chromodynamics, non-perturbative observables such as the low-lying spectrum of hadrons can be extracted from the theory discretized on a Euclidean space-time lattice and simulated on a computer. Real-time quantities on the other hand, such as phase shifts, time-like form factors, or transport properties at finite temperature, cannot be straightforwardly computed. In some cases however real-time effects leave signatures in the Euclidean theory which can be isolated in certain kinematical regimes. I describe several examples of this type at zero and finite-temperature. |

15. 04. 2011 at 09:30S2 15/134 | ## Theorie-SeminarProf. Dr. Jan Pawlowski () Dense and hot QCD and dilute cold quantum gases both define extremes of matter in terms of density and temperature. While cold quantum gases are by now experimentally very well accessible, dense and hot QCD is probed indirectly by e.g. heavy ion collisions and astrophysical observations. |

15. 04. 2011 at 08:30S2 15/134 | ## Theorie-SeminarProf. Dr. Thomas Papenbrock (University of Tennessee/Oak Ridge National Laboratory) Atomic nuclei and trapped atom gases provide us with ample opportunities to study relevant and interesting correlations in finite quantum systems. This seminar reports on recent progress in the model-independent computation of atomic nuclei, with a focus on exotic nuclei and towards heavier masses. In addition, I will present a new effective theory for deformed rotational nuclei and present analytical solutions for the yrast states of mixtures of rotating Bose-Einstein condensates. |

14. 04. 2011 at 15:00S2 15/134 | ## Theorie-SeminarPD Dr. Lorenz von Smekal (TU Darmstadt) Strongly interacting matter fuels the stars and makes up almost the entire mass of the luminous universe. The underlying theory of quarks and gluons, Quantum Chromodynamics (QCD), completely specifies the interactions. However, these are so complex and non-linear that they have yet to be fully understood. Indeed, it is these strong interactions which under normal conditions confine quarks and gluons into the interior of hadrons. Understanding the generation of their masses, the confinement of quarks and gluons, the different phases of QCD at extreme temperatures or densities and the transitions between them are some of the great challenges in physics. In this talk I will discuss and illustrate universal aspects of chiral symmetry restoration and the deconfinement transition, and I will briefly describe where we are heading when investigating the QCD phase diagram with ab-inito non-perturbative QCD methods. |

14. 04. 2011 at 14:00S2 15/134 | ## Theorie-SeminarDr. Paul Romatschke () Compact stars offer a unique window of cold nuclear matter in the regime of extremely high densities. In particular, it has long been speculated that "exotic" phases of nuclear matter, such as quark matter could exist in the core of neutron stars. Lacking the tools to solve QCD accurately for densities expected in compact stars, simple toy models such as the MIT bag model for the QCD equation of state have been state of the art for the past 30 years. In this talk, I will argue that one can do better than that by using recent results from perturbative QCD. In fact, matching modern quark matter to realistic hadronic equations of state, one can reproduce available observations of neutron stars without any fine-tuning of parameters. I will discuss the implications on the cold nuclear matter equation of state and present and future compact star observations. |

14. 04. 2011 at 13:00S2 15/134 | ## Theorie-SeminarProf. Dr. Lucas Platter () The description of strongly interacting few- and many-body systems is a constant challenge to theory. Effective field theories provide one path to the description of such systems provided a ratio of separated scales is available that can be exploited as an expansion parameter. I will discuss the application of EFTs to light nuclei and give overview over recent developments. I will furthermore address how this EFT can also be applied to halo nuclei and few- and many-body systems of ultracold atoms. If time permits I will also raise (and answer) the question how very heay nuclei can be described in a similar systematic fashion. |

14. 04. 2011 at 09:30S2 15/134 | ## Theorie-SeminarDr. Joaquin Drut (Los Alamos National Laboratory) From electrons in graphene to quarks inside neutrons and protons, the realm of strongly-interacting quantum mechanics is filled with fascinating phenomena, unexpected connections and unresolved issues. Indeed, while much is known about fermions in general in weakly-interacting regimes, it is only with the advent of new experimental techniques and modern computational methods (analytic, numerical and mixed) that we are truly starting to understand even the simplest strongly-interacting systems. |

14. 04. 2011 at 08:30S2 15/134 | ## Theorie-SeminarProf. Dr. Hans-Werner Hammer () I will discuss few-body systems near the unitary limit of infinite scattering length. Such systems can be described in an expansion around the ideal scale invariant limit. If three or more particles are present, the (approximate) scale invariance can be anomalous and log-periodic scaling behavior can be observed. I will show some applications in nuclear and particle physics as well as ultracold atoms. |

28. 03. 2011 at 13:00S2 11/207 | ## Theorie-PalaverSam Edwards (TU Darmstadt) A few years ago, Freeman Dyson asked the question if it is possible to detect a single graviton in a realistic experimental setting. The answer to this question is linked to the relevance of quantizing gravity. In this Palaver, I will present a paper (arXiv: gr-qc/0601043) that discusses the possibility of detecting a single graviton. I intend to present the salient points of the paper, but leave plenty of room for (fiery) discussions. Please read the paper and be prepared! |

25. 03. 2011 at 11:15S2 15/134 | ## Theorie-SeminarDr. Axel Maas () The elementary constituents of nuclei are the quarks, which are 'glued' together by the gluons, the mediators of the strong nuclear force. Under extreme conditions, like in the very early universe or supposedly in the interior of neutron stars, this strong force changes its characteristics. To understand this is an ongoing theoretical endeavor. After a brief introduction to this project, a bottom-up approach to the quantum version of the strong interactions, QCD, will be presented. It will be discussed how quarks and gluons can be described both in the vacuum and in extreme conditions. Using this framework, information about the phase diagram of this theory will be deduced. |

25. 03. 2011 at 09:00S2 15/134 | ## Theorie-Seminar (CERN) Calculating bulk properties of Quantum field theories with large interaction strengths is a big challenge for theoretical physics. Examples are QCD matter in the early universe, in neutron stars or in heavy ion collisions but also condensed matter systems like ultra- cold quantum gases. In my talk I will describe an approach to these problems using modern renormalization group methods. |

24. 03. 2011 at 11:15S2 15/134 | ## Theorie-SeminarDr. Kai Hebeler (Ohio State University) Renewed interest in the physics of nuclei is stimulated by experiments at rare isotope facilities which open the way to new regions of exotic nuclei and by astrophysical observations and simulations of neutron stars and supernovae, which require controlled constraints on the equation of state of nucleonic matter. The interplay of chiral effective field theory, renormalization group methods and rapidly increasing computer power are enabling the development of new many-body methods to successfully attack these problems. |

24. 03. 2011 at 09:00S2 15/134 | ## Theorie-SeminarDr. Alexandros Gezerlis (University of Washington) In this talk I will discuss two general areas: a) the physics of heavy nuclei and its connection with the understanding of weak coupling in quantum many-body theory, and b) the physics of neutron-star crusts at intermediate to strong coupling. |

23. 03. 2011 at 14:00S2 15/134 | ## Theorie-SeminarDr. Jens Braun () The theory of the strong interaction, Quantum Chromodynamics (QCD), describes the generation of hadronic masses and the state of hadronic matter during the early stages of the evolution of the universe. While heavy-ion collision experiments provide us with information on hot and dense QCD, experiments with ultracold fermionic atoms provide a clean environment to test our understanding of the dynamical formation of condensates and the generation of bound states in strongly interacting systems. |

18. 03. 2011 at 13:15S2 15/134 | ## Theorie-SeminarDr. Chihiro Sasaki (FIAS) I will present theoretical and phenomenological aspects of Quantum Chromodynamics, a gauge theory of the strong interaction of quarks and gluons composing hadrons. Selected issues are discussed with particular emphasis on the model buildings to be tested in heavy-ion collisions and/or nuclear astrophysics observations. |

14. 03. 2011 at 13:00S2 14/401 | ## Theorie-PalaverDavid Mesterhazy (TU Darmstadt) I will be discussing some aspects related to gravity in three dimensions. We will see why it is an interesting model to look at and on the way, a few surprises will appear. |

22. 02. 2011 at 10:30S2 11/207 | ## Theorie-SeminarPierre Capel () The study of nuclear structure far from stability has been enabled by the development of radioactive-ion beams. This technical breakthrough has led, among other things to the discovery of halo nuclei. These nuclei are light neutron-rich nuclei that exhibit a strongly clusterized structure: they can be viewed as a core that contains most of the nucleons, to which one or two neutrons are loosely-bound. Owing to their low separation energy, these neutrons tunnel far from the classically-allowed region and form a sort of a halo around the core. |

21. 02. 2011 at 13:00S2 14/401 | ## Theorie-Palaver (TU Darmstadt) The non-equlibrium dynamics of quantum fields is relevant for a variety of physical problems. In general this requires non-perturbative techniques as to secular divergences arising in a perturbative treatment. |

18. 02. 2011 at 11:00S2 11/207 | ## Theorie-SeminarA. Rothkopf (Tokyo University) |

10. 02. 2011 at 14:00S2 11/207 | ## Theorie-SeminarK. Kashiwa () |

07. 02. 2011 at 13:00S2 14/401 | ## Theorie-PalaverPiotr Piasecki (TU Darmstadt) Today I will give a short introduction to the functional Renormalization Group. I will explain its basic concepts and will derive the famous Wetterich Equation. After that this Equation will be applied to a simple example. |

25. 01. 2011 at 12:30S2 11/207 | ## Lunch Club SeminarUbirajara van Kolck (University of Arizona) A new generation of experiments is being planned with a significant improvement in the sensitivity to electric dipole moments (EDMs) of the nucleon and light nuclei. Possible signals in any of these measurements would reflect time-reversal violation (TV) beyond that stemming from the phase of the CKM matrix. Could we then infer the origin of TV at the quark/gluon level? |

24. 01. 2011 at 13:00S2 14/401 | ## Theorie-PalaverDr Jean-Sebastien Gagnon (TU Darmstadt) In this Palaver I will present some fundamental concepts of baryogenesis. Starting with a brief review of observational evidences for an asymmetric universe, I will go through the necessary conditions a model must have in order to produce a baryon asymmetry (Sakharov conditions) and show if the Standard Model has "what it takes"' to explain it. |

20. 01. 2011 at 14:00S2 11/207 | ## Theorie-Seminar () |

13. 01. 2011 at 14:00S2 11/207 | ## Theorie-SeminarS. Borsanyi (Wuppertal) |

21. 12. 2010 at 16:00S2 14/401 | ## Christmas Palaver (TU Darmstadt) |

13. 12. 2010 at 13:00S2 14/401 | ## Theorie-Palaver (TU Darmstadt) I will start with the Higgs mechanism and the Higgs boson in the electroweak sector of the standard model. There the (rather aesthetic) fine-tuning problem occurs, which has become a reason for theorists to consider theories beyond the current standard model. I will therefore try to sketch the ideas concerning the Higgs boson in technicolour and supersymmetry. |

07. 12. 2010 at 12:30S2 11/207 | ## Lunch Club SeminarJeremy Holt () |

30. 11. 2010 at 12:30S2 11/207 | ## Lunch Club SeminarLisa Marie Haas (Uni Heidelberg) |

29. 11. 2010 at 13:00S2 14/401 | ## Theorie-PalaverHannes Basler (TU Darmstadt) Starting with a sketch of the Proof of Existence of Color Superconductivity, I will discuss the most symmetric pairing pattern in three-flavor quark matter, the color-flavor locked (CFL) phase, also showing how stress on CFL pairs leads to less symmetric pairing patterns. After these general consideration I will give an short overview of the different approaches to describe color superconductivity, for some reason focusing on the NJL model. |

23. 11. 2010 at 12:30S2 11/207 | ## Lunch Club SeminarAlexander E. Dorokhov (JINR, Dubna) |

09. 11. 2010 at 12:30S2 11/207 | ## Lunch Club SeminarJens Andersen (University Trondheim) We calculate the thermodynamic functions of a quark-gluon plasma for general N_c and N_f to three-loop order using hard-thermal-loop perturbation theory. At this order, all the ultraviolet divergences can be absorbed into renormalizations of the vacuum, the HTL mass parameters, and the strong coupling constant.We show that at three loops, the results for the pressure and trace anomaly are in very good agreement with recent lattice data down to temperatures around 2T_c. |

02. 11. 2010 at 12:30S2 11/207 | ## Lunch Club SeminarDavid Weir (Imperial College London) |

01. 11. 2010 at 13:00S2 14/401 | ## Theorie-Palaver (TU Darmstadt) After having introduced the 2PI effective action in the first part of this introduction, I will explain why it is so well suited for nonequilibrium QFT. Special emphasis will be placed on the implementation of the statistical aspects of nonequilibrium physics and the differences to vacuum and thermal QFT. The aim is then to derive the evolution equations of certain propagators which contain important information about the nonequilibrium evolution of a given system. |

26. 10. 2010 at 12:30S2 11/207 | ## Lunch Club SeminarFranziska Synatschke (Uni Jena) Theories which allow for dynamical supersymmetry breaking have been subject to many investigations. But most approximations to solve these models break supersymmetry explicitly. The functional renormalization group equations allow an approach that leaves supersymmetry unbroken. A manifestly supersymmetric exact renormalization flow will be presented for a scalar theory in two dimensions. The considered model allows for dynamical supersymmetry breaking. The phase diagramm will be discussed as well as the fixed-point structure of the ERG flow which shows an interesting connection to the supersymmetry breaking. |

18. 10. 2010 at 13:00S2 14/401 | ## Theorie-Palaver (TU Darmstadt) The topic will be centered around the following key words: Geometrical quantization, quantization of the Riemann sphere as an example, spinor geometry, Hopf fibration and monopole harmonics. |

04. 10. 2010 at 13:00S2 14/401 | ## Theorie-Palaver (TU Darmstadt) I will give a brief introduction to phenomenological aspects of Dyson-Schwinger Equations and will concentrate on the application of that approach to hadronic contributions to the g-2 of the muon. |

20. 09. 2010 at 13:00S2 14/401 | ## Theorie-PalaverNils Strodthoff (TU Darmstadt) I will give a brief introduction to anomalies in quantum field theory. As an example I will consider the chiral anomaly. I want to show that anomalies are not just a theoretical peculiarity but on the one hand have direct experimental consequences and on the other hand impose strong constraints on gauge theories via the requirement of anomaly cancellation. |

13. 09. 2010 at 13:00S2 14/401 | ## Theorie-PalaverStefano Carignano (TU Darmstadt) Why are heavy quark observables so interesting in the heavy ion business? How can we extract some information on the properties of the Quark-Gluon plasma from them? What have we discovered so far? This, and much more, after a short commercial break. |

27. 08. 2010 at 11:00S2 11/207 | ## Theorie-SeminarDr. Hiro Fujii (Tokyo University) I will start with a general introduction to heavy ion physics and motivate the problem of pre-equilibrium time-evolution and gauge field instabilities, and then discuss the possible roles of the Nielsen-Olesen instabilities toward thermalization. |

00. 00. 0000 at 00:00 |

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