Abstract

It is shown that if (M,φ,α) is a W^*-dynamical system with M a type I von Neumann algebra then the entropy of α w.r.t. φ equals the entropy of the restriction of α to the center of M. If furthermore (N,ψ,β) is a W^*-dynamical system with N injective then h_φ×ψ(α × β) = h_φ(α) + h_ψ(β).

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