Extensions of Representable Positive Linear Functionals to Unitized Quasi *-Algebras

It is known that, under certain conditions, *-representability and extensibility to the unitized *-algebra of a positive linear functional, defined on a *-algebra without unit, are equivalent. In this paper, a new condition for an analogous result is given for the case of a hermitian linear functional defined on a quasi *-algebra ${(\mathfrak{A}, \mathfrak{A}_0)}$ without unit.     

What is the Absolutely Convergent Series

<正>In this section we are going to take a look at a very special series,which the signs of the terms switch back and forth irregularly.It means the series without positive terms and alternating series.Now we know the alterna-     

What is the Absolutely Convergent Series

<正>In this section we are going to take a look at a very special series,which the signs of the terms switch back ancd forth irregularly.It means the series without positive terms and alternating series.Now     

Informativeness of Linear Functionals

In this paper, we study the informativeness of linear functionals in reconstruction problems and obtain exact orders of the informativeness of linear functionals in the Besov and Sobolev classes W and SW.     

Measurable Functionals and Finitely Absolutely Continuous Measures on Banach Spaces

We consider the structure of orthogonal polynomials in the space L ₂(B, ) for a probability measure on a Banach space B. These polynomials are described in terms of Hilbert–Schmidt kernels on the space of square-integrable linear functionals. We study the properties of functionals of this sort. Certain probability measures are regarded as generalized functionals on the space (B, ).     

Metric Entropy of Subsets of Absolutely Convergent Fourier Series

We estimate the metric entropy of compact subsets of the algebra A of absolutely convergent Fourier series     

A Note on Spaces of Absolutely Convergent Fourier Transforms

Let \({\mathcal {F}}f\) be an abolutely convergent Fourier transform on the real line. We extend the following result of K. Karlander to \({\mathbf {R}^{n}}\) for \(n \ge 1\) : Any closed reflexive subspace \(\{ {\mathcal {F}}f \}\) of the space of continuous functions vanishing at infinity is of finite dimension.     

Unbounded Disjointness Preserving Linear Functionals

Let X be a locally compact Hausdorff space and C ₀(X) the Banach space of continuous functions on X vanishing at infinity. In this paper, we shall study unbounded disjointness preserving linear functionals on C ₀(X). They arise from prime ideals of C ₀(X), and we translate it into the cozero set ideal setting. In particular, every unbounded disjointness preserving linear functional of c ₀ can be constructed explicitly through an ultrafilter on complementary to a cozero set ideal. This ultrafilter method can be extended to produce many, but in general not all, such functionals on C ₀(X) for arbitrary X. We also make some remarks where C ₀(X) is replaced by a non-commutative C*-algebra.     

The Universality of an Absolutely Convergent Series on Short Intervals

Siberian Mathematical Journal - Under consideration is a&nbsp;Dirichlet series depending on a&nbsp;parameter and absolutely convergent in the right half of the critical strip. We prove that...     

Field Extensions and Extensions of Linear Differential Operators

Let K R P be a tower of fields, N be a P-module, and : R N be a K-linear differential operator. The aim of this paper is to investigate whether the operator has an extension to P, i.e. if these exists a differential operator : P N such that |_R = . The results of this paper were published in Russian in Mat. Zametki 30(2) (1981), 237–248.     

Antichains and Linear Extensions

Order - When {1, 2,..., m} is an antichain in a poset on m + n points, how should the other n points be arranged to maximize the proportion of linear extensions in which 1 &;gt; 2 &;gt;...     

Positive Functionals on some Spaces of Fractions

The aim of this work is to study norm preserving extensions of positive functionals on some spaces of fractions. The main result is stated in the case of unitary complex Banach algebras with involution. Moreover, we deal with C*-algebras and the commutative case as well. An application is also given.     

Convexity Theories V: Extensions of Absolutely and Totally Convex Modules

The theories of absolutely and totally convex modules are commutative theories and have many properties in common with the theory of modules. Therefore a typical module theoretic notion, namely extensions, is investigated here in these theories. Because of the close connections with Banach spaces extensions of Banach spaces are considered, too.     

Christoffel Transforms and Hermitian Linear Functionals

In this contribution we are focused on some spectral transformations of Hermitian linear functionals. They are the analogues of the Christoffel transform for linear functionals, i. e. for Jacobi matrices which has been deeply studied in the past. We consider Hermitian linear functionals associated with a probability measure supported on the unit circle. In such a case we compare the Hessenberg matrices associated with such a probability measure and its Christoffel transform. In this way, almost unitary matrices appear. We obtain the deviation to the unit matrix both for principal submatrices and the complete matrices respectively.     

Linear Functional-Differential Equations with Absolutely Unstable Solutions

Ukrainian Mathematical Journal - For linear functional-differential equations of retarded and neutral types with infinitely many deviations and self-adjoint operator coefficients, we establish...     

Representable Linear Functionals on Partial *-Algebras

A GNS-like *-representation of a partial *-algebra \mathfrak A{{\mathfrak A}} defined by certain representable linear functionals on \mathfrak A{{\mathfrak A}} is constructed. The study of the interplay with the GNS construction associated with invariant positive sesquilinear forms (ips) leads to the notions of pre-core and of singular form. It is shown that a positive sesquilinear form with pre-core always decomposes into the sum of an ips form and a singular one.