NJL model in Four Dimension at Finite Temperature, Chemical Potentialand   Curvature
  Two flavor Nambu-Jona-Lasinio model with N components is studied in curved space time at finite temperature and density in the leading 1/N expansion. In four space time dimension the model exhibits first order phase transition for positive curvature. Whereas in flat space an increase in temperature induces a second order phase transition even at finite density, in curved space the transition becomes first order. We obtain the phase boundary in density-temperature plane and exhibit its behavior with changing curvature. A three dimensional plot of the phase boundary in $\mu$-T-R space is drawn. 
Ashok Goyal, Meenu Dahiya