Location: Cyclotron Building (434), Seminar Room
Dr. Stefan Leupold, Gießen University, Germany
Weinberg sum rules, four-quark condensates and chiral restoration
Abstract:
In QCD, weighted averages (moments) of the difference of spectra in the vector and axial-vector channel can be identified as order parameters of chiral symmetry breaking (generalized Weinberg sum rules [1]). One of these moments is connected to a specific four-quark condensate. It is pointed out how this condensate can be evaluated for in-medium situations in the large-N_c limit, where N_c denotes the number of colors [2].
The four-quark condensate is evaluated
For the first two cases it is demonstrated that the corrections to the respective large-N_c result can be expected to be small. The third case allows the determination of a transition line to the chirally restored phase as a function of temperature and baryo-chemical potential [4]. The regime of sizable temperature and sizable baryo-chemical potential is especially relevant for the Compressed Baryonic Matter (CBM) project [5] at the future Facility for Antiproton and Ion Research (FAIR) at GSI.
[1] J. I. Kapusta and E. V. Shuryak, Phys. Rev. D 49, 4694 (1994),
hep-ph/9312245.
[2] S. Leupold, Phys. Lett. B 616, 203 (2005), hep-ph/0502061.
[3] P. Gerber and H. Leutwyler, Nucl. Phys. B 321, 387 (1989).
[4] S. Leupold, in preparation.
[5] http://www.gsi.de/zukunftsprojekt/experimente/CBM/