Entanglement in nonequilibrium systems is considered. A general definition
for entanglement measure is introduced, which can be applied for characterizing
the level of entanglement produced by arbitrary operators. Applying this
definition to reduced density matrices makes it possible to measure the
entanglement in nonequilibrium as well as in equilibrium statistical systems.
An example of a multimode Bose-Einstein condensate is discussed.Comment: 10 pages, Late
