Organizers: | Michael Buballa, Lorenz von Smekal |
---|---|

Date: | Tuesdays, 12:00 |

Room: | S2|11 10 or S2|11 207 |

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Technische Universität Darmstadt

Institut für Kernphysik

Theoriezentrum

S2|11

Schlossgartenstraße 2

64289 Darmstadt