Results 311 to 320 of about 4,584,260 (359)

Essential Norms of Composition Operators

Integral Equations and Operator Theory, 2004
Recently, there has been considerable interest in studying lower and upper estimates for the essential norms of composition operators in function spaces. Sometimes, as a consequence, a necessary and sufficient condition for the composition operator to be compact on the function space can be obtained.
Gorkin, Pamela, MacCluer, Barbara D.
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GEOMETRIC QUANTITIES OF COMPOSITION OPERATORS

Far East Journal of Mathematical Sciences (FJMS), 2017
Summary: In this paper, we investigate geometric quantities of composition operators associated with various subclasses of univalent functions in the unit disk. We also consider applications of the quantities.
Kim, Yong Chan, Choi, Jae Ho
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Composition operators on potential spaces

Proceedings of the American Mathematical Society, 1992
By a result of B. Dahlberg, the composition operators T H f = H ∘ f {T_H}f = H \circ f need not be bounded on some of the Sobolev spaces (or spaces of Bessel potentials) even for very smooth functions H = H
Adams, David R., Frazier, Michael
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Commutators of composition operators with adjoints of composition operators on the ball

Complex Variables and Elliptic Equations, 2015
In this paper, we investigate compactness of the commutator on the Hardy space or the weighted Bergman space (), when and are automorphisms of the unit ball . We obtain that is compact if and only if both and are unitary and they commute. This generalizes the corresponding result in one variable. Moreover, our technique is different and simple.
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On Algebras Generated by Composition Operators

Canadian Journal of Mathematics, 1974
Let Δ be the open unit disk in the complex plane and let be the group of automorphisms of Δ onto Δ, define byThe Banach spaces Hp = Hp(Δ), 1 ≦ p < ∞, are the Hardy spaces of functions analytic in Δ with their integral p means bounded,
Cima, J. A., Wogen, W. R.
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ON P-HYPONORMAL COMPOSITION OPERATORS

Universal Journal of Mathematics and Mathematical Sciences, 2020
Summary: In this paper, we introduce P-hyponormal composition operators on \(L^2\)-spaces and study some of their properties. We show that Fuglede-Putnam's (briefly FP) theorem holds for P-hyponormal and P-hyponormal composition operators.
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Operator regularization and composite operators

Canadian Journal of Physics, 1990
We demonstrate how operator regularization can be used to compute radiative corrections to Green's functions involving composite operators. No divergences are encountered and no symmetry-breaking regulating parameter need be introduced into the initial Lagrangian.
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The Norms of Compositions of Arithmetic Operators

Bulletin of the London Mathematical Society, 1987
Weighted inequalities which widely generalize the Turán-Kubilius inequality are established. The following is typical: Let w(m) be a non- negative real-valued arithmetic function which satisfies w(q) \(\ll 1\), w(qm) \(\ll w(q)w(m)\) uniformly for prime-powers q and positive integers m, \((q,m)=1\).
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Analytic Toeplitz and Composition Operators

Canadian Journal of Mathematics, 1972
This paper is a continuation of [1] where we began the study of intertwining analytic Toeplitz operators. Recall that X intertwines two operators A and B if XA = BX. Let H2 be the Hilbert space of analytic functions in the open unit disk D for which
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Co-Rank of a Composition Operator

Canadian Mathematical Bulletin, 1986
AbstractA composition operator CT on L2(X, Σ,m) is a bounded linear transformation induced by a mapping T : X → X via CTf = f∘ T.If m has no atoms then the co-rank of CT (i.e., dim is either zero or infinite. As a corollary, when m has no atoms, CT is a Fredholm operator iff it is invertible.
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