Curvature invariant on noncommutative polyballs

In this paper we develop a theory of curvature (resp. multiplicity) invariant for tensor products of full Fock spaces F2(Hn1)⊗⋯⊗F2(Hnk)F2(Hn1)⊗⋯⊗F2(Hnk) and also for tensor products of symmetric Fock spaces Fs2(Hn1)⊗⋯⊗Fs2(Hnk). This is an attempt to find a more general framework for these invariants and extend some of the results obtained by Arveson for the symmetric Fock space, by the author and Kribs for the full Fock space, and by Fang for the Hardy space H2(Dk)H2(Dk) over the polydisc. To prove the existence of the curvature and its basic properties in these settings requires a new approach based on noncommutative Berezin transforms and multivariable operator theory on polyballs and varieties, as well as summability results for completely positive maps. The results are presented in the more general setting of regular polyballs.