Darmstadt 2008 – wissenschaftliches Programm

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HK: Fachverband Physik der Hadronen und Kerne

HK 49: Theorie

HK 49.3: Vortrag

Freitag, 14. März 2008, 14:30–14:45, 2F

Thermodynamics of a non-local NJL-type model (was HK 34.68 before) — •Thomas Hell, Simon Rößner, and Wolfram Weise — Physik Department, TU München, 85748 Garching, Germany

From hadron spectroscopy it follows that the SU(2) chiral symmetry of the QCD-Lagrangian is dynamically broken at low energies. Pions appear as the corresponding Goldstone bosons. A simple scheme including these properties is the Nambu–Jona-Lasinio (NJL) model, where the quark interaction is described by a local four fermion coupling. Due to this locality loop integrals are divergent and the model is non-confining. Asymptotic freedom is implemented crudely through a regularizing cut-off at approximately 1 GeV. This limits the applicability of the NJL model to a momentum range below that cut-off.

In our work we want to include asymptotic freedom in a more realistic way. For this reason we use a non-local Lagrangian including an effective momentum-dependent four-fermion vertex. This allows for the matching of the low-momentum region to perturbative QCD in the high-momentum regime.

We apply this model to QCD thermodynamics, incorporating couplings to a gluonic background field. The chiral condensate serves as an order parameter for the chiral phase transition while the confinement-deconfinement transition is described by the Polyakov loop. The resulting thermodynamic potential and related quantities are calculated and compared with results from lattice QCD.

Work supported in part by BMBF, GSI, and DFG Excellence Cluster “Origin and Structure of the Universe”.