An abstract approach to some spectral problems of direct sum differential operators.
An amalgamation of the Banach spaces associated with James and Schreier, Part I: Banach-space structure
We create a new family of Banach spaces, the James-Schreier spaces, by amalgamating two important classical Banach spaces: James' quasi-reflexive Banach space on the one hand and Schreier's Banach space giving a counterexample to the Banach-Saks property on the other. We then investigate the properties of these James-Schreier spaces, paying particular attention to how key properties of their 'ancestors' (that is, the James space and the Schreier space) are expressed in them. Our main results include...
An analytic representation for selfmaps of a countably infinite set and its cycles. (Short Communication).
An analytic representation for selfmaps of a countably infinite set and its cycles.
An integral extrapolation theorem with applcations
An IntroduCtion into the Theory of Sequence Spaces and Measures of Noncompactness
An operator characterization of -spaces in a class of Orlicz spaces
We consider an embedding of the group of invertible transformations of [0,1] into the algebra of bounded linear operators on an Orlicz space. We show that if this embedding preserves the group action then the Orlicz space is an -space for some 1 ≤ p < ∞.
An operator-theoretic approach to truncated moment problems
We survey recent developments in operator theory and moment problems, beginning with the study of quadratic hyponormality for unilateral weighted shifts, its connections with truncated Hamburger, Stieltjes, Hausdorff and Toeplitz moment problems, and the subsequent proof that polynomially hyponormal operators need not be subnormal. We present a general elementary approach to truncated moment problems in one or several real or complex variables, based on matrix positivity and extension. Together...
An overview of some recent developments on the Invariant Subspace Problem
This paper presents an account of some recent approaches to the Invariant Subspace Problem. It contains a brief historical account of the problem, and some more detailed discussions of specific topics, namely, universal operators, the Bishop operators, and Read’s Banach space counter-example involving a finitely strictly singular operator.
Application of sequential shifts to an interpolation problem.
In the present paper initial operators for a right invertible operator, which are induced by sequential shifts and have the property c(R) are constructed. An application to the Lagrange type interpolation problem is given. Moreover, an example with the Pommiez operator is studied.
Asymptotically cyclic quasianalytic contractions
The study of quasianalytic contractions, motivated by the hyperinvariant subspace problem, is continued. Special emphasis is put on the case when the contraction is asymptotically cyclic. New properties of the functional commutant are explored. Analytic contractions and bilateral weighted shifts are discussed as illuminating examples.
Asymptotically holomorphic functions and translation invariant subspaces of weighted Hilbert spaces of sequences
is generated in strong operator topology by two of its elements
Backward extensions of hyperexpansive operators
The concept of k-step full backward extension for subnormal operators is adapted to the context of completely hyperexpansive operators. The question of existence of k-step full backward extension is solved within this class of operators with the help of an operator version of the Levy-Khinchin formula. Some new phenomena in comparison with subnormal operators are found and related classes of operators are discussed as well.
Bicontractive projections in sequence spaces and a few related kinds of maps
Boundedness of Riesz potential generated by generalized shift operator on spaces
In this paper, the boundedness of the Riesz potential generated by generalized shift operator from the spaces to the spaces is examined.
Certain invariant subspaces for operators with rich eigenvalues.
Cesàro wedge and weak Cesàro wedge -spaces
In this paper we deal with Cesàro wedge and weak Cesàro wedge -spaces, and give several characterizations. Some applications of these spaces to general summability domains are also studied.
Characterization of Matrix Operators on Orlicz Spaces.
Characterizing Fréchet-Schwartz spaces via power bounded operators
We characterize Köthe echelon spaces (and, more generally, those Fréchet spaces with an unconditional basis) which are Schwartz, in terms of the convergence of the Cesàro means of power bounded operators defined on them. This complements similar known characterizations of reflexive and of Fréchet-Montel spaces with a basis. Every strongly convergent sequence of continuous linear operators on a Fréchet-Schwartz space does so in a special way. We single out this type of "rapid convergence" for a sequence...