Components of linear-fractional composition operators
نویسندگان
چکیده
منابع مشابه
Norms of Linear-fractional Composition Operators
We obtain a representation for the norm of the composition operator Cφ on the Hardy space H 2 whenever φ is a linear-fractional mapping of the form φ(z) = b/(cz + d). The representation shows that, for such mappings φ, the norm of Cφ always exceeds the essential norm of Cφ. Moreover, it shows that a formula obtained by Cowen for the norms of composition operators induced by mappings of the form...
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If φ is an analytic function mapping the unit disk D into itself, the composition operator Cφ is the operator on H 2 given by Cφf = f ◦φ. The structure of the composition operator Cφ is usually complex, even if the function φ is fairly simple. In this paper, we consider composition operators whose symbol φ is a linear fractional transformation mapping the disk into itself. That is, we will assu...
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We characterize the essentially normal composition operators induced on the Hardy space H2 by linear fractional maps; they are either compact, normal, or (the nontrivial case) induced by parabolic non-automorphisms. These parabolic maps induce the first known examples of nontrivially essentially normal composition operators. In addition we characterize those linearfractionally induced compositi...
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We give a new proof that every linear fractional map of the unit ball induces a bounded composition operator on the standard scale of Hilbert function spaces on the ball, and obtain norm bounds analogous to the standard one-variable estimates. We also show that Cowen’s one-variable spectral radius formula extends to these operators. The key observation underlying these results is that every lin...
متن کاملSpectrum and essential spectrum of linear combinations of composition operators on the Hardy space H2
Let -----. For an analytic self-map --- of --- , Let --- be the composition operator with composite map --- so that ----. Let --- be a bounded analytic function on --- . The weighted composition operator --- is defined by --- . Suppose that --- is the Hardy space, consisting of all analytic functions defined on --- , whose Maclaurin cofficients are square summable. .....
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ژورنال
عنوان ژورنال: Journal of Mathematical Analysis and Applications
سال: 2003
ISSN: 0022-247X
DOI: 10.1016/s0022-247x(03)00004-0