Michael Buballa, Technical University Darmstadt
Towards a stability analysis of inhomogeneous phases in QCD
QCD inspired models, like the Nambu--Jona-Lasinio (NJL) model, suggest that the phase diagram of strong-interaction matter at moderate densities could contain regions, where the chiral condensate varies in space. A powerful method to identify these inhomogeneous phases is a stability analysis, in which the stability of the energetically preferred homogeneous state against small inhomogeneous fluctuations is investigated. Recent systematic studies of this kind have led to the suspicion that the inhomogeneous phases could be cutoff artifacts related to the nonrenormalizablity of these models. This calls for a clarification of this issue directly within QCD. In my talk I discuss a new approach for a stability analysis that is based on the two-particle irreducible effective action and compatible with full QCD calculations within the framework of Dyson-Schwinger equations. When applying this method to the NJL model we recover the result of the conventional stability analysis. For QCD the analysis is more difficult due to the nonlocality of the quark selfenergy. Preliminary results within a simple truncation will be presented.