  As is well-known, spontaneous CP-violation in the strong interaction is
possible at theta = pi, which is commonly referred to as Dashen's phenomenon.
This phenomenon has been studied extensively using chiral Lagrangians. Here the
two-flavor NJL model at theta = pi is discussed. It turns out that the
occurrence of spontaneous CP-violation depends on the strength of the 't Hooft
determinant interaction, which describes the effect of instanton interactions.
The dependence of the phase structure, and in particular of the CP-violating
phase, on the quark masses, temperature, baryon and isospin chemical potential
is examined in detail. The latter dependence shows a modification of the
charged pion condensed phase first discussed by Son and Stephanov.
