OPUS 4 | Universitätspublikationen

The finite-temperature phase structure of lattice QCD with twisted-mass Wilson fermions (2008)

Ernst-Michael Ilgenfritz Karl Jansen Maria Paola Lombardo Michael Müller-Preussker Marcus Petschlies Owe Philipsen Lars Zeidlewicz

We report progress in our exploration of the finite-temperature phase structure of two-flavour lattice QCD with twisted-mass Wilson fermions and a tree-level Symanzik-improved gauge action for a temporal lattice size Nt = 8. Extending our investigations to a wider region of parameter space we gain a global view of the rich phase structure. We identify the finite temperature transition/ crossover for a non-vanishing twisted-mass parameter in the neighbourhood of the zerotemperature critical line at sufficiently high b . Our findings are consistent with Creutz’s conjecture of a conical shape of the finite temperature transition surface. Comparing with NLO lattice cPT we achieve an improved understanding of this shape.

Probing the composition of sub-millisecond rotating compact stars by r-modes instability (2008)

Giuseppe Pagliara Alessandro Drago

We investigate the implications of the r-modes instability on the composition of a compact star rotating at a sub-millisecond period. In particular, the only viable astrophysical scenario for such an object, wich might present inside the Low Mass X-ray Binary associated with the x-ray transient XTE J1739-285, is that it has a strangeness content. Since previous analysis indicate that hyperonic stars or stars containing a kaon condensate are unlikely because of the mass-shedding constraint, the only remaining possibility is that such an object is either a strange quark star or a hybrid quark-hadron star.

Astrophysical Implications of the QCD phase transition (2008)

Jürgen Schaffner-Bielich Irina Sagert Matthias Hempel Giuseppe Pagliara Tobias Fischer Anthony Mezzacappa Friedrich-Karl Thielemann Matthias Liebendörfer

The possible role of a first order QCD phase transition at nonvanishing quark chemical potential and temperature for cold neutron stars and for supernovae is delineated. For cold neutron stars, we use the NJL model with nonvanishing color superconducting pairing gaps, which describes the phase transition to the 2SC and the CFL quark matter phases at high baryon densities. We demonstrate that these two phase transitions can both be present in the core of neutron stars and that they lead to the appearance of a third family of solution for compact stars. In particular, a core of CFL quark matter can be present in stable compact star configurations when slightly adjusting the vacuum pressure to the onset of the chiral phase transition from the hadronicmodel to the NJL model. We show that a strong first order phase transition can have strong impact on the dynamics of core collapse supernovae. If the QCD phase transition sets in shortly after the first bounce, a second outgoing shock wave can be generated which leads to an explosion. The presence of the QCD phase transition can be read off from the neutrino and antineutrino signal of the supernova.

The adjoint potential in the pseudoparticle approach: string breaking and Casimir scaling (2008)

Christian Szasz Marc Wagner

We perform a detailed study of the adjoint static potential in the pseudoparticle approach, which is a model for SU(2) Yang-Mills theory. We find agreement with the Casimir scaling hypothesis and there is clear evidence for string breaking. At the same time the potential in the fundamental representation is linear for large separations. Our results are in qualitative agreement with results from lattice computations.

Status of ETMC simulations with Nf = 2+1+1 twisted mass fermions (2008)

Rémi Baron Philippe Boucaud Albert Deuzeman Vincent Drach Federico Farchioni Vicent Gimenez Gregorio Herdoiza Karl Jansen István Montvay David Palao Elisabetta Pallante Olivier Pène Siebren Reker Enno E. Scholz Carsten Urbach Marc Wagner Urs Wenger

We present the status of runs performed in the twisted mass formalism with Nf =2+1+1 flavours of dynamical fermions: a degenerate light doublet and a mass split heavy doublet. The procedure for tuning to maximal twist will be described as well as the current status of the runs using both thin and stout links. Preliminary results for a few observables obtained on ensembles at maximal twist will be given. Finally, a reweighting procedure to tune to maximal twist will be described.

Static-light meson masses from twisted mass lattice QCD (2008)

Karl Jansen Chris Michael Andrea Shindler Marc Wagner

We compute the static-light meson spectrum using two-flavor Wilson twisted mass lattice QCD. We have considered five different values for the light quark mass corresponding to 300MeV<~ mPS<~ 600MeV. We have extrapolated our results, to make predictions regarding the spectrum of B and Bs mesons.

Ordnung für den Bachelor- und den Masterstudiengang Physik der Johann Wolfgang Goethe-Universität vom 26.02.2008 : genehmigt durch Beschluss des Präsidiums der Johann Wolfgang Goethe-Universität vom 25.03.2008 (2008)

Studienordnung für den Bachelor- und den Master-Studiengang Physik der Informationstechnologie an der Johann Wolfgang Goethe-Universität Frankfurt am Main mit dem Abschluss Bachelor of Science (B.Sc.) bzw. Master of Science (M.Sc.) vom 14. Januar 2004 in der Fassung vom 16. Juli 2007 : genehmigt mit Erlass vom 28. September 2007, Az.: III 1.3 – 422/13/10.010 – (0002) (2008)

Prüfungsordnung für die Bachelor- und Master-Studiengänge Physik der Informationstechnologie der Johann Wolfgang Goethe-Universität Frankfurt am Main mit dem Abschluss Bachelor of Science (B.Sc.) bzw. Master of Science (M.Sc.) vom 14.01.2004 in der Fassung vom 16. Juli 2007 : genehmigt mit Erlass vom 28.September 2007, Az.: III 1.3 - 422/13/10.010 – (0002) (2008)

Fachspezifischer Anhang zur SPoL (Teil III): Studienfach Physik in den Studiengängen L2 und L5 (2008)

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