ON THE FINITE-SIZE OF THE BAG AND THE CRITICAL DECONFINING TEMPERATURE IN HYBRID MODELS

We consider a chiral bag model at finite temperature, with a thermal skyrmion of Eskola and Kajantie modelling the exterior sector. Supposing that the ''Cheshire Cat'' scenario takes care of all zero temperature effects, we show the existence of a critical temperature over which there can only exist a quark-gluon plasma phase, since the bag is no longer stable. This fact is interpreted as the occurrence of a deconfinement phase transition. It turns out that the critical temperature has an important dependence on the boundary conditions, due to the finite size of the bag, obeyed by the quarks and gluons of the thermal vacuum inside the bag. In fact, the corrections due to these boundary conditions imply a critical temperature bigger by almost a factor two compared to the case where the boundary conditions are ignored.