### A hyperbolic universal operator commuting with a compact operator

Carl Cowen, Eva Gallardo-Gutiérrez
Published: 1 February 2022

Abstract: A Hilbert space operator is called universal (in the sense of Rota) if every operator on the Hilbert space is similar to a multiple of the restriction of the universal operator to one of its invariant subspaces. We exhibit an analytic Toeplitz operator whose adjoint is universal in the sense of Rota and which commutes with a quasinilpotent, injective, compact operator with dense range, but unlike other examples, it acts on the Bergman space instead of the Hardy space and this operator is associated with a “hyperbolic” composition operator.
Keywords: Hilbert / commuting / hyperbolic / universal operator / compact / space operator / quasinilpotent / adjoint / invariant / Hardy

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