  The phase diagram of the massive chiral Gross-Neveu model (the
1+1-dimensional Nambu-Jona-Lasinio model at large N) is investigated in the
vicinity of the tricritical point. Using the derivative expansion, the grand
canonical potential is cast into the form of a Ginzburg-Landau effective
action. Minimization of this action by variational and numerical methods
reveals both 1st and 2nd order phase transitions to a chiral crystal phase,
separated by a tricritical line. These findings are contrasted to the massive
Gross-Neveu model with discrete chiral symmetry where only 2nd order
transitions have been observed.
