  We elucidate the close relationship between spontaneous time-reversal
symmetry breaking and the physics of excitonic instabilities in strongly
correlated multiband systems. The underlying mechanism responsible for the
spontaneous breaking of time-reversal symmetry in a many-body system is closely
related to the Cooper-like pairing instability of interband particle-hole pairs
involving higher order symmetries. Studies of such pairing instabilites have,
however, mainly focused on the mean-field aspects of the virtual exciton
condensate, which ignores the presence of the underlying collective Fermi
liquid excitations. We show that this relationship can be exploited to
systematically derive the coupling of the condensate order-parameter to the
intraband Fermi liquid particle-hole excitations. Surprisingly, we find that
the static susceptibility is negative in the ordered phase when the coupling to
the Fermi liquid collective excitations are included, suggesting that a uniform
condensate of virtual excitons, with or without time reversal breaking, is an
unstable phase at T=0.

Strongly Correlated Electrons