  We review a recently introduced unified approach to the analytical
quantification of correlations in Gaussian states of bosonic scalar fields by
means of Renyi-2 entropy. This allows us to obtain handy formulae for
classical, quantum, total correlations, as well as bipartite and multipartite
entanglement. We apply our techniques to the study of correlations between two
modes of a scalar field as described by observers in different states of
motion. When one or both observers are in uniform acceleration, the quantum and
classical correlations are degraded differently by the Unruh effect, depending
on which mode is detected. Residual quantum correlations, in the form of
quantum discord without entanglement, may survive in the limit of an infinitely
accelerated observer Rob, provided they are revealed in a measurement performed
by the inertial Alice.
