  It is shown that the work fluctuations and work distribution functions are
fundamentally different in systems with short-range versus long-range
correlations. The two cases considered with long- range correlations are
magnetic work fluctuations in an equilibrium isotropic ferromagnet, and work
fluctuations in a non-equilibrium fluid with a temperature gradient. The
long-range correlations in the former case are due to equilibrium Goldstone
modes, while in the latter they are due to generic non-equilibrium effects. The
magnetic case is of particular interest since an external magnetic field can be
used to tune the system from one with long-range correlations, to one with only
short- range correlations. It is shown that in systems with long-range
correlations the work distribution is extraordinarily broad compared to systems
with only short-range correlations. Surprisingly these results imply that
fluctuations theorems such as the Jarzynski fluctuation theorem are more useful
in systems with long-range correlations than in systems with short-range
correlations.
