  In the massive chiral Gross-Neveu model, a phase boundary separates a
homogeneous from an inhomogeneous phase. It consists of two parts, a second
order line and a first order line, joined at a tricritical point. Whereas the
first order phase boundary requires a full, numerical Hartree-Fock calculation,
the second order phase boundary can be determined exactly and with less effort
by a perturbative stability analysis. We extend this stability analysis to
higher order perturbation theory. This enables us to locate the tricritical
point exactly, without need to perform a Hartree-Fock calculation. Divergencies
due to the emergence of spectral gaps in a spatially periodic perturbation are
handled using well established tools from many body theory.
