  We investigate the effects of the external gravitational and constant
magnetic fields to the dynamical symmetrybreaking. As simple models of the
dynamical symmetry breaking we consider the Nambu-Jona-Lasinio (NJL) model and
the supersymmetric Nambu-Jona-Lasinio (SUSY NJL) model non-minimally
interacting with the external gravitational field and minimally interacting
with constant magnetic field. The explicit expressions for the scalar and
spinor Green functions are found up to the linear terms on the spacetime
curvature and exactly for a constant magnetic field. We obtain the effective
potential of the above models from the Green functions in the magnetic field in
curved spacetime. Calculating the effective potential numerically with the
varying curvature and/or magnetic fields we show the effects of the external
gravitational and magnetic fields to the phase structure of the theories. In
particular, increase of the curvature in the spontaneously broken chiral
symmetry phase due to the fixed magnetic field makes this phase to be less
broken. On the same time strong magnetic field quickly induces chiral symmetry
breaking even at the presence of fixed gravitational field within nonbroken
phase.
