The Nambu Jona-Lasinio model with density dependent U_A(1) anomaly

by Dr Hiroaki Kohyama (Academia Sinica, Taiwan)

Thursday 28 Jan 2010, 14:30 → 15:30 Asia/Kolkata

AG-69 (Colaba Campus)

Whether the phase transition from chiral broken phase to chiral restored state is of the first order is an interesting question. To study this, we use the Nambu Jona-Lasinio model which is believed to be a low energy effective theory of quantum chromodynamics (QCD). In this work, we consider the density dependent U_A(1) anomaly and study the critical surface in the quark mass and chemical potential space. We have found that the surface shrinks when a quark chemical potential increases, which is the opposite result from the study by using usual NJL model. The difference comes from the density dependence of the U_A(1) anomaly and our result is consistent to the recent lattice QCD study. Our result suggest the restoration of the U_A(1) anomaly at high density, which seems to be physically reasonable because a colour superconductivity state may dominate at intermediate baryon density where the U_A(1) anomaly should be negligible.