NAMBU-JONA-LASINIO MODEL IN CURVED SPACE-TIME

The phase structure of Nambu-Jona-Lasinio model with N-component fermi ons in curved space-time is studied in the leading order of the 1/N ex pansion. The effective potential for composite operator psipsiBAR is c alculated by using the normal coordinate expansion in the Schwinger pr oper-time method. The existence of the first order phase transition ca used by the change of the space-time curvature is confirmed and the dy namical mass of the fermion is calculated as a simultaneous function o f the curvature and the four-fermion coupling constant. The phase diag ram in the curvature and the coupling constant is obtained.