Organizers: | Almudena Arcones, Jens Braun, Michael Buballa, Hans-Werner Hammer, Gabriel Martínez-Pinedo, Robert Roth, Achim Schwenk, Lorenz von Smekal, Jochen Wambach |
---|---|

Date: | Thursdays, 14:00 |

Room: | S2|11 10 |

04. 07. 2024 at 13:30S2 11/10 | ## Theorie-SeminarDean Lee (MSU) I give an introduction to a new machine learning approach called parametric matrix models, which are based on the matrix equations of quantum physics rather than the biology of neurons. Rather than fitting output functions according to some specified form, PMMs learn the underlying equations that produce the desired output, similar |

26. 06. 2024 at 13:30S2 11/10 | ## Theorie-SeminarShinya Wanajo (Albert Einstein Institute Potsdam) The origin of r-process elements such as gold and uranium has long been a mystery in astrophysics. The discovery of an electromagnetic counterpart (kilonova) associated with the gravitational wave event GW170817 has confirmed that neutron star mergers are sites where the r-process occurs. However, whether neutron star mergers are the dominant sources of r-process nuclei in the universe remains uncertain. In this presentation, I will share our latest nucleosynthesis study results, which are based on magnetohydrodynamic simulations of neutron star mergers, as well as other potential sites such as black hole-neutron star mergers and collapsars. |

13. 06. 2024 at 13:30S2 11/10 | ## Theorie-SeminarMelissa Mendes (TU Darmstadt) Investigating the behavior of the nuclear equation of state (EOS) is an open research question. In particular, the study of neutron stars has been especially fruitful to probe the EOS at densities above saturation thanks to observations of its properties such as mass, radius, tidal deformability and temperature. In this talk, I discuss two works dealing with constraining the neutron star EOS. First, I use observations of the luminosity of fast cooling transiently-accreting neutron stars to investigate a possible first-order quark-hadron phase transition. Then, I discuss how new NICER mass-radius data combined with gravitational wave observations and chiral effective theory constraints provide information for the neutron star EOS. |

06. 06. 2024 at 13:30S2 11/10 | ## Theorie-SeminarAndrea Porro (TU Darmstadt) Giant monopole resonances have a long-standing theoretical importance in nuclear structure. The interest resides notably in the so-called breathing mode that has been established as a standard observable to constrain the nuclear incompressibility. The Random Phase Approximation (RPA) within the frame of phenomenological Energy Density Functionals (EDF) has become the standard tool to address giant resonances and extensive studies, have been performed throughout the years. A proper study of collective excitations within the ab initio framework is, however, missing. Additionally, the ab initio many-body methods developed over the past two decades encounter limitations when it comes to dealing with excited-state properties. |

02. 05. 2024 at 13:30S2 11/10 | ## Theorie-SeminarSilas Beane (University of Washington) After reviewing the unitary Fermi gas and relevant aspects of non-relativistic conformal symmetry (Schroedinger symmetry), I will introduce the superfluid effective field theory (EFT) that describes the Fermi gas at and near unitarity in the far infrared. This EFT admits a large-charge expansion which allows the systematic computation of large-charge n-point functions. I will discuss the potential relevance of the large-charge formalism to the study of special nuclear reactions with many low-energy neutrons in the final state. |

18. 04. 2024 at 13:30S2 11/10 | ## Theorie-SeminarLotta Jokiniemi (TRIUMF) Neutrinoless double-beta decay is a hypothetical weak-interaction process in which two neutrons inside an atomic nucleus simultaneously transform into protons and only two electrons are emitted. Since the electrons are emitted without accompanying antiparticles, the process violates the lepton-number conservation and requires that neutrinos are Majorana particles, hence providing unique vistas in the physics beyond the Standard Model of particle physics. The potential to discover new physics drives ambitious experimental searches around the world. However, extracting interesting physics from the experiments relies on nuclear-theory predictions, which remain a major obstacle. |

08. 02. 2024 at 13:30S2 11/10 | ## Theorie-SeminarRob Pisarski (Brookhaven National Laboratory) In QCD, the eta prime meson is heavy because the breaking of the anomalous U_A(1) symmetry is large. A simple argument suggests that it should then be easy to see a first order chiral transition for light quarks. Nevertheless, numerical simulations on the lattice see no evidence for such a first order chiral transition. I suggest that this occurs because the usual power counting for anomalous operators is more subtle than expected. This leads to numerous predictions for different numbers of quark flavors. The case of a single flavor is especially interesting. It also suggests novel experimental signals. |

25. 01. 2024 at 13:30S2 11/10 | ## Theorie-SeminarIsak Svensson (TU Darmstadt) The theory of the strong interaction - quantum chromodynamics (QCD) - is unsuited to practical calculations of nuclear observables and approximate models for nuclear interaction potentials are required. In contrast to phenomenological models, chiral effective field theories (chiral EFTs) of QCD grant a handle on the theoretical uncertainty arising from the truncation of the chiral expansion. Uncertainties in chiral EFT are preferably quantified using Bayesian inference, but quantifying reliable posterior predictive distributions for nuclear observables presents several challenges. First, chiral EFT is parametrized by unknown low-energy constants (LECs) whose values must be inferred from low-energy data of nuclear structure and reaction observables. There are 31 LECs at fourth order in Weinberg power counting, leading to a high-dimensional inference problem which I approach by developing an advanced sampling protocol using Hamiltonian Monte Carlo (HMC). This allows me to quantify LEC posteriors up to and including fourth chiral order. Second, the chiral EFT truncation error is correlated across independent variables such as scattering energies and angles; I model correlations using Gaussian processes. Third, the computational cost of computing few- and many-nucleon observables typically precludes their direct use in Bayesian parameter estimation as each observable must be computed in excess of 10^5 times during HMC sampling. However, eigenvector-continuation emulators today provide the necessary leverage to include observables beyond the two-nucleon sector in Bayesian inferences. In this talk I discuss the progress I made in this area during my PhD studies, presenting findings regarding the LEC inference problem as well as resulting posterior predictive distributions for nuclear observables. |

14. 12. 2023 at 13:30S2 11/10 | ## Theorie-SeminarSoeren Schlichting (Bielefeld University) High-energy heavy-ion collisions provide a unique environment to explore the properties of strong-interaction matter under extreme conditions. Since the theoretical description of the complex reaction dynamics from the underlying theory of QCD poses an outstanding challenge, a macroscopic description in relativistic hydrodynamics is commonly employed to describe the emergence of collective phenomena in heavy-ion collisions. In this talk, we will discuss recent progress to understand the non-equilibrium dynamics of QCD plasmas from kinetic theory, and assess the range of applicability of hydrodynamics as an effective description for non-equilibrium systems. |

07. 12. 2023 at 13:30S2 11/10 | ## Theorie-SeminarMariam Gogilashvili (Florida State University) At the end of their lives, most massive stars undergo core collapse. Some stars explode as a core-collapse supernova (CCSN) explosion leaving behind neutron stars (NS) while others fail to explode and collapse to stellar-mass black holes (BH). One of the major challenges in CCSN theory is to predict which stars explode and which fizzle. We develop an analytic force explosion condition (FEC) to predict which massive stars explode. The FEC depends upon four dimensionless parameters only: 1. net neutrino heating deposited in the gain region, 2. neutrino opacity that parameterizes the neutrino optical depth in the accreted matter near the neutron-star surface, 3. the integrated buoyant driving, and 4. the radial component of the Reynolds stress. The FEC promises to be an accurate explosion condition for multi-dimensional simulations as well as being useful diagnostic to measure a "distance" to explosion. I will present a progress in validating the FEC with multi-dimensional simulations and discuss potential to expand the model by including additional effects that may be important to predict explosions in nature |

30. 11. 2023 at 13:30S2 11/10 | ## Theorie-SeminarMarta Molero (Universita degli studi di Trieste) Modelling the evolution of the elements in galaxies of different morphological types is a multidisciplinary and challenging task. Chemical evolution simulations must be able to follow ~ 13 billion years of evolution of a galaxy and also to keep track of the elements synthesized and ejected from every astrophysical site of interest. In this talk, I will give a general overview of the Chemical Evolution of Galaxies field describing both its aims and explaining which are the basic ingredients necessary to build a Chemical Evolution simulation. I will then focus on the main topic of my PhD: the study of the evolution of heavy elements abundances. The majority of elements beyond the Fe peak are produced by neutron capture processes which can be rapid (r-process) or slow (s-process) with respect to the beta-decay in nuclei. Understanding which are the astrophysical formation sites of these two processes has become one of the major challenges in chemical evolution. The s-process mainly takes place in low-intermediate mass stars during the asymptotic giant branch phase and in rotating massive stars, with the latter being particularly relevant at low metallicities. On the other hand, the r-process sites are still under debate, with possible main producers candidates being peculiar supernovae (magneto-rotational supernovae, MR-SNe) or merging of compact objects (neutron stars or neutron star-black hole). Although observations point towards merging neutron stars (MNS) as the major astrophysical r-process site, chemical evolution simulations still struggle to reproduce the abundance pattern of the [Eu/Fe] vs. [Fe/H] (with Eu being a typical r-process element) if MNS are the only producers of r-process material and realistic timescales for merging are assumed. In this talk, I will first present the main steps done in chemical evolution simulations to understand the origin of neutron capture elements and then I will show results from our latest work. We studied both the abundance patterns and the radial gradients of nine neutron-capture elements (Y, Zr, Ba, La, Ce, Eu, Mo, Nd, Pr) in the Galactic thin disc by means of a detailed two-infall chemical evolution model with state-of-the-art nucleosynthesis and timescales prescriptions. We compared our results with data from the sixth data release of the Gaia-ESO survey, which consists of 62 open clusters located at different Galactocentric distances and with ages ranging from 0.1 to 7 Gyr, and 1300 disc field stars, in order to underline which are the main uncertainties still present in the modelling of heavy elements. |

23. 11. 2023 at 13:30S2 11/10 | ## Theorie-Seminar Johannes Weber (Humboldt-Universitaet Berlin) The hot nuclear medium that permeated the early universe can be studied experimentally with heavy-ion collisions and through various theoretical approaches. New or upgraded experiments turn our attention to hard processes and a more fine-grained resolution of this primordial state of matter. In this endeavor quarkonia, open heavy flavors, and jets turn out to be versatile probes, which are usually described through models based on resummed perturbative QCD, AdS, and effective field theories. The lattice provides nonperturbative input and constraints to such models. In-medium bottomonia, the complex static quark-antiquark potential, as well as the heavy-quark momentum and the jet transverse momentum diffusion transport coefficients are key quantities where lattice gauge theory has recently achieved significant progress with major impact for heavy-ion phenomenology. I review these lattice results, relate them to phenomenological applications, and close with an outlook towards expectations for the next few years. |

16. 11. 2023 at 13:30S2 11/10 | ## Theorie-SeminarTheo F. Motta (TU Darmstadt and JLU Giessen) Understanding the phase structure of Quantum Chromodynamics (QCD) is of paramount importance for nuclear and particle physics. At large densities and low temperatures, many complex phases are expected to appear. This is where the lattice sign problem is unavoidable and extrapolation methods such as Taylor expansions are out-of-bounds. Alongside colour-superconductivity, quarkyonic matter, and so on, the possibility of a crystalline phase has been studied for over twenty years. In simplified models of QCD such as NJL or quark-meson models, these phases are present. However, no unambiguous determination exists that they appear in QCD. In this talk, I will discuss our efforts to develop a method of stability analysis that is compatible with full QCD via Dyson-Schwinger Equations. |

09. 11. 2023 at 13:30S2 11/10 | ## Theorie-SeminarMartin Obergaulinger (Valencia University) Magnetic fields are a common feature of both the progenitors of core-collapse supernovae, i.e., massive stars, and of their remnants, neutron stars. If combined with rapid rotation, they can affect the explosion dynamics and eject a part of the gas in the form of jets along the rotational axis. Besides the high explosion energies, these events also differ from the majority of neutrino-driven supernovae by their nucleosynthetic yields and observables like the gravitational-wave signal. I will present recent simulations of a set of three-dimensional simulations combining magnetohydrodynamics and neutrino transport in which explosions with different degree of magnetic influence occur and highlight some of the key processes that determine the outcome. |

10. 08. 2023 at 14:00S2 11/10 | ## Theorie-SeminarAman Abhishek (Institute of Mathematical Sciences, Chennai, India) Mean-field model quantum field theories of hadrons were traditionally developed to describe cold and dense nuclear matter and are by now very well constrained from the recent neutron star merger observations. We show that when augmented with additional known hadrons and resonances but not included earlier, these mean-field models can be extended beyond its regime of applicability. Calculating some specific ratios of baryon number susceptibilities for finite temperature and moderate values of baryon densities within mean-field approximation, we show that these match consistently with the lattice QCD data available at lower densities, unlike the results obtained from a non-interacting hadron resonance gas model. We also estimate the curvature of the line of constant energy density, fixed at its corresponding value |

28. 06. 2023 at 14:00S2 11/10 | ## Theorie-SeminarMark Alford (Washington University, St. Louis) In a neutron star merger, nuclear matter experiences dramatic changes in temperature and density that happen in milliseconds. Mergers therefore probe dynamical properties that may help us uncover the phase structure of ultra-dense matter. I will describe some of the relevant material properties, focusing on chemical (beta) equilibration and its consequences such as bulk viscosity and damping of oscillations. |

22. 06. 2023 at 14:00S2 11/10 | ## Theorie-SeminarDam T. Son (University of Chicago) We develop a formalism of nonrelativistic conformal field theory, which is then used to describe neutrons at low energies. We show that the rates of nuclear reactions with emission of a few neutrons in the final state show a power-law behavior in the kinematic region where the emitted neutrons have almost the same momentum. We show how corrections to this power-law behavior can be computed using conformal perturbation theory. |

15. 06. 2023 at 14:00S2 11/10 | ## Theorie-SeminarAssistant Prof. Dr. Luka Leskovec |

25. 05. 2023 at 14:00S2 11/10 | ## Theorie-SeminarSara Collins (Regensburg) Numerous ongoing experimental investigations into physics beyond the Standard Model focus on nucleons as fundamental probes, prompting extensive efforts to extract nucleon structure observables on the lattice. This includes the determination of quantities like the weak charges and axial form factors. However, it is also interesting to extend such studies to hyperons, which have received less attention. Exploring the properties of hyperons provides valuable insights into the SU(3) flavor symmetry encoded in low-energy effective field theory descriptions. Moreover, studying their weak decays offers alternative means of determining the elements of the CKM matrix. As a first step we determine the spectrum, weak charges and sigma terms of the baryon octet controlling all sources of systematic uncertainty. |

24. 04. 2023 at 11:00S2 11/207 | ## Theorie-SeminarFrederic Noel (Uni Bern) Mu->e conversion in nuclei gives one of the leading limits on BSM lepton-flavor violating (LFV) processes. In this process a muon bound to a nucleus converts into an electron without neutrinos. Upcoming measurements call for a more consistent theoretical description of mu->e conversion, which can be done model independently using an effective field theory frame work in terms of effective BSM operators. As it turns out, the relevant operators for the spin dependent part of mu->e conversion also mediates LFV pseudoscalar decays, which makes it possible to relate these processes and their experimental limits. Furthermore for the treatment of the bound state physics appearing in mu->e conversion, quantifiable knowledge on the charge densities of the considered nuclei is needed. |

20. 04. 2023 at 14:00S2 11/10 | ## Theorie-SeminarSaga Aurora Saeppi (TU Muenchen) With LIGO and its friends observing colliding neutron stars, and astrophysicists measuring their radii and masses with unprecedented precision, understanding how dense QCD matter behaves is a particularly timely goal. I will approach this from the side of (very-)high-density theory: How do first-principles calculations in dense QCD in the small-coupling limit work, and how have they advanced in the last few years? Some of the advancements I will discuss in this talk include an efficient and simple way to incorporate the effects of quark masses in perturbative calculations, particularly useful for near-future calculations of the bulk viscosity, as well as an ongoing computation of the next-to-next-to-next-to-leading order pressure of cold dense QCD, where there are both concrete recent (and upcoming) results for the self-energy as well as improved theoretical methods necessary for finishing the full computation. |

26. 01. 2023 at 14:00zoom | ## Theorie-SeminarZhonghao Sun (Oak Ridge National Laboratory) Precise and predictive calculations of the atomic nuclei from realistic nuclear force help us to understand how the fundamental interaction leads to the emergence of various exotic phenomena. The advances in computational power, emerging machine learning technology, and the development of many-body methods make it possible to perform uncertainty quantification and sensitivity analyses in the nuclear structure calculations. In this talk, I will report the progress of the ab-initio coupled-cluster method in describing spherical and deformed atomic nuclei. I will also introduce the quantified predictions of the neutron skin thickness of 208Pb and the drip line of oxygen isotopes. |

15. 12. 2022 at 15:00zoom | ## Theorie-SeminarAgnieszka Sorensen (INT Seattle) The equation of state (EOS) of dense nuclear matter has been the center of numerous research efforts over the years. While numerous studies indicate that the EOS is relatively soft around the saturation density of nuclear matter, recent analyses of neutron star data strongly suggest that in the cores of neutron stars, where densities may reach several times that of normal nuclear matter, the EOS becomes very stiff - so stiff, in fact, that the speed of sound squared may substantially exceed the conformal limit of 1/3. This striking behavior inspires the research I will present in this talk. |

24. 11. 2022 at 14:00S2 11/10 | ## Theorie-SeminarOwe Philipsen (GU Frankfurt) Recently, an emerging chiral spin symmetry was discovered in the multiplets of lattice QCD hadron correlators for a temperature window above the chiral crossover. This symmetry is larger than the expected |

10. 11. 2022 at 14:00S2 11/10 | ## Theorie-SeminarFrithjof Karsch (Bielefeld University) Lattice QCD calculations at non-zero temperature and with non-vanishinq |

27. 10. 2022 at 14:00S2 11/10 | ## Theorie-SeminarRenwick James Hudspith (GSI) The g-2 of the muon provides a high-precision test of the Standard Model of particle physics, and a possible window into beyond the Standard Model physics. Currently, there is some tension between the theoretical prediction of this quantity and experiment. As experimental precision continues to improve it is paramount for theoretical computations to do so also, in hope of resolving this tension. One of the most poorly-known contributions to the theory calculation of the muon g-2 comes from hadronic light-by-light scattering. I will present an overview of our measurement of this contribution using lattice QCD techniques, where we have obtained the most precise determination to date. |

23. 09. 2022 at 14:00S2 11/10 (plus zoom) | ## Theorie-SeminarBaha Balantekin (University of Wisconsin, Madison) Entanglement of constituents of a many-body system is a recurrent feature of quantum behavior. Quantum information science provides tools, such as the entanglement entropy, to help assess the amount of entanglement in such systems. Many-neutrino systems are present in core-collapse supernovae, neutron star mergers, and the Early Universe. Recent work in applying the tools of quantum information science to the description of the entanglement in astrophysical many-neutrino systems is presented, in particular the connection between entropy and spectral splits in collective neutrino oscillations is elaborated. |

14. 07. 2022 at 14:00S2 11/10 (plus zoom) | ## Theorie-SeminarDerek Teaney (Stony Brook) To motivate the simulations I review Lattice data on the chiral phase transition in QCD. Then I discuss the hydrodynamics of the chiral phase transition, reviewing the appropriate dynamical equations above, below, and during the phase transition. Then a present a simulation of the dynamics of the phase transition, which shows how goldstone modes appear dynamically. Finally I discuss soft pions in heavy ion collisions, which are enhanced relative to normal hydrodynamic simulations of heavy ion collisions. I suggest that this reflects the fingerprints of the O(4) critical point. |

07. 07. 2022 at 14:00S2 11/10 (plus zoom) | ## Theorie-SeminarLorenz von Smekal (Uni Giessen) The real-time methods discussed and compared in this talk include classical-statistical lattice simulations, the Gaussian state approximation (GSA), and the functional renormalization group (FRG) formulated on the Keldysh closed-time path. The quartic anharmonic oscillator coupled to an external heat bath after Caldeira and Leggett thereby serves as an illustrative example where a benchmark solution can be obtained from exact diagonalization with constant Ohmic damping. To extend the GSA to open systems, we solve the corresponding Heisenberg-Langevin equations in the Gaussian approximation. For the real-time FRG, we introduce a novel general prescription to construct causal regulators based on introducing scale-dependent fictitious heat baths. As first field theory applications we have used our real-time FRG framework to calculate dynamical critical exponents for different dynamics. |

04. 07. 2022 at 15:00S2 11/10 (plus zoom) | ## Theorie-SeminarDr. Robert Pisarski (Brookhaven National Laboratory) I discuss some combination of topics in SU(N) gauge theories at nonzero temperature and density, including: the exact solution of the low energy excitations for cold, dense quarks in 1+1 dimensions (you'll learn what a Luttinger liquid is); how to represent timelike Wilson loops in Hamiltonian form (bit obvious after the fact); configurations with topological charge 1/N in SU(N) gauge theories without dynamical quarks. |

09. 06. 2022 at 14:00S2 11/10 (plus zoom) | ## Theorie-SeminarCarolyn Raithel (Princeton Center for Theoretical Science) Binary neutron star mergers provide a unique probe of the dense-matter equation of state (EOS) across a wide range of parameter space, from the cold EOS during the inspiral to the finite-temperature EOS following the merger. In this talk, I will discuss the influence of finite-temperature effects on the post-merger evolution of a neutron star coalescence. I will present a new set of neutron star merger simulations, which use a phenomenological framework for calculating the EOS at arbitrary temperatures and compositions. I will show how varying the properties of the particle effective mass affects the thermal profile of the post-merger remnant and how this, in turn, and influences the post-merger evolution. Finally, I will discuss several ways in which a future measurement of the post-merger gravitational waves can be used to constrain the dense-matter EOS. |

02. 06. 2022 at 14:00S2 11/10 (plus zoom) | ## Theorie-SeminarJoanna Sobczyk (Uni Mainz) We are entering an era of high-precision neutrino oscillation experiments (T2HK, DUNE), which potentially hold answers to some of the most exciting questions in particle physics. Their scientific program requires a precise knowledge of neutrino-nucleus interactions coming from fundamental nuclear studies. Ab initio many-body theory has made great advances in the last years and is able to give relevant predictions for medium-mass nuclei important for the neutrino experiments. |

31. 05. 2022 at 16:00S2 11/10 (plus zoom) | ## Theorie-SeminarAleksas Mazeliauskas (CERN) The emergence of macroscopic medium properties over distances much smaller than a single atom is a fascinating and non-trivial manifestation of the many-body physics of Quantum Chromodynamics in high-energy nuclear collisions. The observation of collective particle behaviour in collisions of heavy-ions at the Relativistic Heavy Ion Collider at BNL and the Large Hadron Collider at CERN is strong evidence that a new exotic phase of matter called the Quark-Gluon Plasma is created in these large collision systems. However, the striking discovery of the very same collective phenomena in much smaller systems of proton-proton and proton-lead collisions at the LHC has confounded heavy-ion physics expectations and is not predicted by the conventional high-energy physics picture of elementary collisions. One of my main research goals is to uncover the physical origins of this universal macroscopic behaviour. In this talk I will review the recent progress and future plans in developing theoretical description and experimental tests of these effects within the non-Abelian quantum field theory of strong interactions. |

12. 05. 2022 at 14:00S2 11/10 (plus zoom) | ## Theorie-SeminarProf. Dr. Thomas Schaefer (North Carolina State University) Recent interest in stochastic fluid dynamics is motivated by the search for a critical point in the QCD phase diagram. I will discuss old ideas about effective actions that have recently received new interest, and some new ideas about how to implement stochastic fluid dynamics in numerical simulations. |

10. 02. 2022 at 14:00zoom | ## Theorie-SeminarLotta Jokiniemi (University of Barcelona) Observing neutrinoless double-beta (0vbb) would undoubtedly be one of the most anticipated breakthroughs in modern-day neutrino and nuclear physics. This is highlighted by the number of massive experiments worldwide trying to detect the phenomenom, as well as the efforts of numerous theory groups trying to probe the process from different theory frameworks. When observed, the lepton-number-violating process would provide unique vistas beyond the Standard model of particle physics. However, the half-life of the process depends on coupling constants whose effective values are under debate, and nuclear matrix elements (NMEs) that have to be extracted from theory. Unfortunately, at present different many-body calculations probe matrix elements whose values disagree by more than a factor of two. Hence, it is crucial to gain a better understanding on both the coupling constants and the NMEs in order to plan future experiments and to extract the beyond-standard-model physics from the experiments. |

03. 02. 2022 at 14:00zoom | ## Theorie-SeminarLaura Sagunski (Goethe Universtaet Frankfurt) The first ever direct detections of gravitational waves from merging black holes and neutron stars by the Laser Interferometer Gravitational-Wave Observatory (LIGO) and the Virgo detector have opened a fundamentally new window into the Universe. Gravitational waves from binary mergers are high precision tests of orbital dynamics and provide an unprecedented tool to probe fundamental physics. Not only do they allow to test gravity under extreme conditions, but also to address the very fundamental open questions in the evolution of our Universe, namely the mysteries of dark matter and dark energy (or possible modifications of general relativity). In my talk, I will show how we can turn binary mergers into cosmic labs where we can test the very foundations of general relativity and explore the existence of new interactions and particles, like axions, which could be the dark matter. |

16. 12. 2021 at 14:00zoom | ## Theorie-SeminarFelipe Attanasio (Uni Heidelberg) The equation of state of hadronic matter is of high importance for |

09. 12. 2021 at 14:00zoom | ## Theorie-SeminarVittorio Soma (CEA Saclay) Recent developments in many-body theory and in the modelling of nuclear Hamiltonians have enabled the ab initio description of a considerable fraction of atomic nuclei up to mass A~100. In this context, one of the main challenges consists in devising a method that can tackle doubly open-shell systems and at the same time scales gently with mass number. This would allow both to access all systems below A~100 and to open up perspectives for extending ab initio calculations to the whole nuclear chart. |

25. 11. 2021 at 14:00zoom | ## Theorie-SeminarNicolas Wink (TU Darmstadt) In this talk we explore the calculation of elementary correlation functions in the context of QCD. We consider these correlation functions in Euclidean and Minkowski space-time. For the latter we consider direct calculations based on dimensional regularization in Dyson-Schwinger equations in a scalar theory and Yang-Mills. Additionally, we present results from analytic continuation of Euclidean lattice data based on Gaussian Process Regression in full QCD. Afterwards we turn our attention to the calculation of transport coefficients in Yang-Mills, based on gluon spectral functions obtained previously. In the last part of the talk we consider field dependencies in functional Renormalization Group equations. We focus in particular on technical challenges at high densities and how to overcome them. |

18. 11. 2021 at 14:00zoom | ## Theorie-SeminarAndreas Ipp (Vienna University of Technology) The earliest stage right after the collision of ultrarelativistic heavy ions is known as the Glasma stage. It is characterized by strong anisotropic color fields and forms the precursor of the quark-gluon plasma. In this talk, I present our approach to simulating the Glasma using a colored particle-in-cell simulation. With this method, we can access the full 3+1 dimensional space-time picture of the collision process. These simulations are inherently plagued by numerical Cherenkov instability, and we show how an improved action can cure this instability using a semi-implicit scheme. Simulation results can be checked in a dilute limit against analytic calculations. I will present results for observables such as the rapidity profile or momentum broadening of jets within the Glasma stage. |

28. 10. 2021 at 14:00zoom | ## Theorie-SeminarWeiguang Jiang (Chalmers) Advances in quantum many-body methods and computing allow us to study the finite nuclei and infinite nuclear matter with realistic interaction models based on chiral effective field theory. We develop the nuclear matter emulators and introduce the robust statistical approach called history matching to explore the non-implausible nuclear-matter predictions with chiral interactions. We studied 1.6*10^6 non-implausible interaction samples in a huge LECs domain and reveal the connection between the finite nuclei and nuclear matter saturation properties. |

10. 06. 2021 at 14:00zoom | ## Theorie-SeminarBastian Kubis (Uni Bonn) The first new experimental results on the anomalous magnetic moment of the muon from Fermilab, published in April 2021, confirm the tension with the Standard Model prediction, now at 4.2 sigma. The uncertainty |

27. 05. 2021 at 14:00zoom | ## Theorie-SeminarCristina Manuel Hidalgo (Instituto de Ciencias del Espacio, Barcelona) Systems made up by massless fermions but with unequal right-handed and left-handed populations have lately attracted great interest |

20. 05. 2021 at 14:00zoom | ## Theorie-SeminarMikhail Stephanov (University of Illinois Chicago) We usually think of hydrodynamics as a deterministic description of |

06. 05. 2021 at 14:00zoom | ## Theorie-SeminarGert Aarts (Swansea University) In recent years applications of machine learning in the physical sciences have increased substantially. In this talk I will discuss some recent developments, starting from "standard" classification problems of phase transitions in statistical physics. This will be followed by giving a physical interpretation of machine learning functions as observables in a statistical system, paving the way to include them in Hamiltonians. Finally, I will speculate on whether our experience in quantum field theory can be exploited to further develop machine learning frameworks. |

22. 04. 2021 at 14:00zoom | ## Theorie-SeminarJose Pons (Universitat d'Alacant) I will review the general theory of long-term thermal evolution of neutron stars (a.k.a. "neutron star cooling") with a special focus on the effects of strong magnetic fields. After discussing the interplay between magnetic and thermal evolution and the observational facts that are usually employed to constrain the theories, I will discuss in some more detail a particular example: the possible observational evidence of the "nuclear pasta" phase, in the inner crust of neutron stars. The main facts leading to our conclusions will be highlighted, with pros and cons. |

04. 02. 2021 at 14:00zoom | ## Theorie-SeminarAndreas Ekstroem (Chalmers University of Technology) Some ab initio nuclear interaction models work better than others and it is not clear why. We are using methods from computational statistics to generate new knowledge about the strong nuclear interaction and our models thereof. In this seminar I will outline some of these methods and present some recent results. I will also present an emulation method that allows for the computation of bulk properties of an atomic nucleus for a million of different model parameters in less than one hour on a standard laptop. The equivalent set of ab-initio coupled-cluster computations would require about 20 years. This speedup enables a range of statistical analyses of nuclear interaction models, and new ways to predict observables across the nuclear chart. |

28. 01. 2021 at 14:15zoom | ## Theorie-SeminarGergeley Endroedi (Uni Bielefeld) Strong magnetic fields are known to have a significant impact on |

21. 01. 2021 at 14:00Zoom | ## Theorie-SeminarTyler Gorda (TU Darmstadt) The cores of massive neutron stars (NSs) may probe an extremely interesting regime of the phase diagram of quantum chromodynamics (QCD): one where the degrees of freedom may change from colorless hadrons to colored quarks and gluons. However, such a region is inaccessible to current nuclear-theory or high-density perturbative QCD (pQCD) techniques. As such, NSs provide an important window into a theoretically inaccessible region of the QCD equation of state (EOS). In this talk, I will discuss two specific topics. First, I will detail our current phenomenological program to constrain the physical properties of the QCD EOS at all densities by extrapolating the known, controlled nuclear and pQCD EOSs to intermediate densities where they can connect with astrophysical NS observables. This allows us to address questions as to the phase of matter inside these objects. Secondly, I will discuss our ongoing effort to improve the convergence of the pQCD EOS, by calculating higher-order corrections to the pressure of cold quark matter. Such an improved EOS would, through our extrapolation program, allow for more stringent constraints on the QCD EOS at all densities. |

14. 01. 2021 at 14:00zoom | ## Theorie-SeminarMaria Paola Lombardo (INFN-Laboratori Nazionali di Frascati) We study the scaling properties of QCD in temperature and mass close to the thermal crossover, and for quark masses ranging from the heavy quark regime to the physical values. The lattice results are obtained in the fixed scale approach, either with anisotropic simulations with Nf=2+1 flavours, and with simulations of Nf=2 +1+1 flavours at maximal twist. We propose a simple combination of chiral observables, which reduces the additive renormalizations and the contribution from the regular terms in the equation of state, thus helping the assessment of the hypothesized universal behaviour. |

10. 12. 2020 at 14:00zoom | ## Theorie-SeminarAlexander Rothkopf (University of Stavanger) The study of quantum systems coupled to an environment plays a vital role in how we measure temperatures of the coldest and hottest matter in the universe. The strategy relies on introducing impurities into the system of interest and on observing how these probe particles evolve towards or in equilibrium with their surroundings, from which we may in turn deduce the thermal properties of that environment. Originally studied in the context of condensed matter physics, open quantum systems nowadays provide a common language to research spanning multiple orders of magnitude in temperature, ranging from Bose Einstein condensates made of ultracold atoms to the Quark-Gluon plasma created in ultra-relativistic collisions of heavy ions. We will explore how polaron impurities in the former and quarkonium particles in the latter are two manifestations of quantum Brownian motion, a phenomenon ideally described by open quantum systems. |

19. 11. 2020 at 14:00zoom | ## Theorie-SeminarParikshit Junnarkar (TU Darmstadt) Lattice QCD has made impressive progress in recent years in spectroscopy of multi-quark states. In this talk, I will present an overview of the lattice QCD methodology in studying multi-quark states. These will be six quark states (two-baryons) and four quark states (tetraquarks). In particular, I will present and discuss results of two-baryon states in the SU(3) singlet channel known as the H-dibaryon and also discuss predictions of exotic two baryon states with heavy quarks. In addition, I will also present an overview of the doubly heavy tetra quark states and its cousins. |

29. 10. 2020 at 14:00zoom | ## Theorie-SeminarTyler Gorda (TU Darmstadt) The cores of massive neutron stars (NSs) may probe an extremely interesting regime of the phase diagram of quantum chromodynamics (QCD): one where the degrees of freedom may change from colorless hadrons to colored quarks and gluons. However, such a region is inaccessible to current nuclear-theory or high-density perturbative QCD (pQCD) techniques. As such, NSs provide an important window into a theoretically inaccessible region of the QCD equation of state (EOS). In this talk, I will discuss two specific topics. First, I will detail our current phenomenological program to constrain the physical properties of the QCD EOS at all densities by extrapolating the known, controlled nuclear and pQCD EOSs to intermediate densities where they can connect with astrophysical NS observables. This allows us to address questions as to the phase of matter inside these objects. Secondly, I will discuss our ongoing effort to improve the convergence of the pQCD EOS, by calculating higher-order corrections to the pressure of cold quark matter. Such an improved EOS would, through our extrapolation program, allow for more stringent constraints on the QCD EOS at all densities. |

22. 10. 2020 at 14:00zoom | ## Theorie-SeminarTanja Hinderer (University of Amsterdam) The gravitational waves from merging binaries carry unique information about the internal structure of compact objects. This is of major interest for neutron stars, offering the possibility for advancing our understanding matter and fundamental interactions in largely unexplored regimes. I will discuss the imprints of neutron star matter on the gravitational waves during the relatively clean, cumulative inspiral epoch, and the need for modeling these effects with a tapestry of approximation schemes for the interplay of dynamical gravity and matter. I will summarize what we have learned from recent measurements and conclude with an outlook onto the remaining challenges and exciting prospects for the next years as gravitational-wave science continues to move towards an era of precision physics. |

13. 02. 2020 at 14:00S2 11/10 | ## Theorie-SeminarSungtae Cho (Kangwon National University) We discuss the production of charmed hadrons in heavy ion collisions based on both the statistical and coalescence models. Starting from the investigation on estimated yields of charmed hadrons in the statistical hadronization model, we consider in the coalescence model transverse momentum distributions of those hadrons produced at quark-hadron phase transition in heavy ion collisions. We also consider the transverse momentum distribution of exotic hadrons such as Tcc and X(3872) mesons, and study transverse momentum distribution ratios between various charmed hadrons. We show that the transverse momentum distribution ratios between charmed hadrons are closely related to not only kinds and numbers of quarks but also the interplay between constituent quarks of those hadrons. We also discuss elliptic flows of charmonium states, and argue the possible relation between elliptic flows and wave function distributions in momentum space. |

06. 02. 2020 at 14:00S2 11/10 | ## Theorie-SeminarErik Olsen (Universite Libre de Bruxelles) Understanding astrophysical observables and phenomena requires a thorough knowledge of various properties of nuclei all over the nuclear chart. Since most of these systems are inaccessible through experiment, theoretical predictions are necessary. At present, nuclear Density Functional Theory is the only method available which can reach these systems while maintaining a microscopic character. Its key ingredient, the nuclear energy density functional, is an effective interaction based on one-body local densities and currents which contains a number of coupling constants whose values are optimized to experimental data and/or pseudo-data. Developing this interaction to minimize its root-mean-square error with respect to certain observables is crucial for more accurate astrophysical predictions. Past procedures in this endeavor will be discussed, as well as current plans to perform fits using Bayesian methodologies. Efforts to incorporate beyond-mean-field effects through the generator coordinate method and odd-mass nuclei into the fitting procedure will also be examined. |

12. 12. 2019 at 14:00S2 11/10 | ## Theorie-SeminarYeunhwan Lim (TU Darmstadt) Nuclear equation of state (EOS) is constructed with energy density functional (EDF) and liquid drop model (LDM) technique. Compared with the classical LDM approach containing alpha particle, deutron, triton, and helio are added to construct nuclear EOS. Energy density functional parameters are constrained by theoretical neutron matter calculation, symmetric nuclear matter properties, and maximum mass of neutron stars. The nuclear surface tension and the critical temperature necessary for the free energy of finite nuclei are calculated in a consistent way. In this talk, I will present and discuss the current results obtained from LDM and EDF with most recent parameters. |

24. 10. 2019 at 14:00S2 11/10 | ## Theorie-SeminarArtem Volosniev (Institute of Science and Technology Austria) Shallow bound states whose spatial extent is significantly larger than the range of the binding potential are often universal, i.e., their properties are independent of the shape of the underlying interactions. These states are often studied because they have no classical counterpart. |

10. 10. 2019 at 14:00S2 11/10 | ## Theorie-SeminarNoriyuki Sogabe (Keio University) We study the static and dynamic critical phenomena near the possible high-density QCD critical point in the superfluid phases of nuclear/quark matter. In particular, we find that its dynamic universality class is different not only from that of the high-temperature QCD critical point between the hadron and quark-gluon-plasma phases, but also from those universality classes studied in condensed matter systems so far. We argue that this novelty stems from the interplay between the chiral criticality and the presence of the superfluid phonon---a feature specific for the high-density QCD critical point. |

05. 09. 2019 at 14:00S2 11/10 | ## Theorie-SeminarJoaquin E. Drut (University of North Carolina) |

04. 07. 2019 at 14:00S2 11/10 | ## Theorie-SeminarDominik Schwarz (Uni Bielefeld) Mannheim's model of conformal gravity is claimed to describe universal properties of galaxy rotation curves without dark matter. In this talk I will discuss the emission of gravitational waves from inspiralling compact binaries in the context of conformal gravity models. These models exhibit both a massless and a massive spin 2 graviton, which makes the analysis of the observed gravitational wave events in these models very different from the generic study in general relativity. An analysis at leading order is performed to show that Mannheim's model can be ruled out from the observation of a merger of two neutron stars. Other parameter regimes of conformal gravity turn out to be indistinguishable from general relativity for the observed gravitational wave events and offer interesting candidate theories for a theory of quantum gravity. |

03. 07. 2019 at 11:00S2 11/10 | ## Theorie-SeminarThomas Schaefer (North Carolina State University) We discuss the role of thermal fluctuations in |

26. 06. 2019 at 11:00S2 11/10 | ## Theorie-SeminarDavid Blaschke (University of Wroclaw) n a recent article [1] we have demonstrated that a first order |

06. 06. 2019 at 14:00S2 11/10 | ## Theorie-SeminarJohann Haidenbauer (Juelich) Over the last few years the Julich-Bonn-Munich Group has performed |

28. 05. 2019 at 13:15S2 11/207 | ## Theorie-SeminarDietrich Roscher (Universitaet Koeln) In the last decades, a plethora of new phenomena and structures has been found in low-energy condensed matter systems that seem to defy the Landau paradigm of phase transitions. Oftentimes, effective theories with certain topological features and fractionalized degrees of freedom are best suited to describe the experimental findings. Unfortunately, writing down such an effective theory and understanding its relation to the accepted microscopic model for the actual material is usually not the same thing. |

09. 05. 2019 at 14:00S2 11/10 | ## Theorie-SeminarJohannes Weber (MSU) Quarkonia within the quark-gluon-plasma have been suggested as an effective thermometer of the hot QCD medium, as their properties are modified due to color screening and thermal dissociation. I discuss correlation functions of spatially separated static quark-antiquark |

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]. |

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. |

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. |

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. |

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. |

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. |

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. |

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. |

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. |

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. |

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. |

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. |

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 |

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 |

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. |

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. |

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 |

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. |

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. |

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 11:00S2 11/10 | ## Theorie-SeminarNoemi Rocco () |

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 () |

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 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. |

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) |

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) |

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) |

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 |

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. |

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. |

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) |

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. |

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

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

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. |

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. |

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. |

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

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) |

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. |

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. |

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 |

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) |

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

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. |

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 |

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. |

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 |

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. |

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. |

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

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 () |

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. |

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. |

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. |

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

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. |

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. |

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. |

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. |

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

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

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

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

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. |

Technische Universität Darmstadt

Institut für Kernphysik

Theoriezentrum

S2|11

Schlossgartenstraße 2

64289 Darmstadt