  Associated to any orthogonal representation of a countable discrete group is
an probability measure-preserving action called the Gaussian action. Using the
Polish model formalism we developed before, we compute the entropy (in the
sense of Bowen, Kerr-Li) of Gaussian actions when the group is sofic.
Computations of entropy for Gaussian actions has only been done when the acting
group is abelian and thus our results are new even in the amenable case.
Fundamental to our approach are methods of noncommutative harmonic analysis and
$C^{*}$-algebras which replace the Fourier analysis used in the abelian case.
