Browsing by Subject "Nordgren, Rosenthal and Wintrobe's Theorem"

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    A new proof of a Nordgren, Rosenthal and Wintrobe Theorem on universal operators
    (American Mathematical Society, 2017) Cowen, Carl C.; Gallardo-Gutiérrez, Eva A.
    A striking result by Nordgren, Rosenthal and Wintrobe states that the Invariant Subspace Problem is equivalent to the fact that any minimal invariant subspace for a composition operator Cφ induced by a hyperbolic automorphism φ of the unit disc D acting on the classical Hardy space H² is one dimensional. We provide a completely different proof of Nordgren, Rosenthal and Wintrobe’s Theorem based on analytic Toeplitz operators.