  We study nonequilibrium fluctuation theorems in the presence of a
time-reversal symmetry-breaking field and nonconservative forces, in a
stochastic as well as a deterministic set up. We consider a system and a heat
bath, called the combined system, and show that the fluctuation theorems are
valid even when the heat bath goes out of equilibrium during driving. The only
requirement for the validity is that, when the driving is switched off, the
combined system relaxes to a state having a uniform probability measure on a
constant energy surface, consistent with microcanonical ensemble of an isolated
system.
