Translation-invariant operators in reproducing kernel Hilbert spaces
arXiv:2109.05879 · doi:10.1007/s00020-022-02705-4
Abstract
Let be a locally compact abelian group with a Haar measure, and be a measure space. Suppose that is a reproducing kernel Hilbert space of functions on , such that is naturally embedded into and is invariant under the translations associated with the elements of . Under some additional technical assumptions, we study the W*-algebra of translation-invariant bounded linear operators acting on . First, we decompose into the direct integral of the W*-algebras of bounded operators acting on the reproducing kernel Hilbert spaces , , generated by the Fourier transform of the reproducing kernel. Second, we give a constructive criterion for the commutativity of . Third, in the commutative case, we construct a unitary operator that simultaneously diagonalizes all operators belonging to , i.e., converts them into some multiplication operators. Our scheme generalizes many examples previously studied by Nikolai Vasilevski and other authors.
36 pages, 1 figure, minor changes and corrections in the second version