paper

Representations of *-semigroups associated to invariant kernels with values continuously adjointable operators

arXiv:1507.06840 · doi:10.1007/s00020-017-2346-1

Abstract

We consider positive semidefinite kernels valued in the -algebra of continuous and continuously adjointable operators on a VH-space (Vector Hilbert space in the sense of Loynes) and that are invariant under actions of -semigroups. For such a kernel we obtain two necessary and sufficient boundedness conditions in order for there to exist -representations of the underlying -semigroup on a VH-space linearisation, equivalently, on a reproducing kernel VH-space. We exhibit several situations when the latter boundedness condition is automatically fulfilled. For example, when specialising to the case of Hilbert modules over locally -algebras, we show that both boundedness conditions are automatically fulfilled and, consequently, this general approach provides a rather direct proof of the general Stinespring-Kasparov type dilation theorem for completely positive maps on locally -algebras and with values adjointable operators on Hilbert modules over locally -algebras.

40 pages

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