Universal K?the Sequence Spaces

 A characterization is given for the K?the matrices B such that the K?the sequence space , with , contains all K?the sequence spaces of order p as subspaces. It follows that the class of K?the sequence spaces of order p has a universal element which is quasinormable. In particular, there is a quasinormable space (respectively, which contains every nuclear Fréchet space with basis (respectively, every countably normed Fréchet Schwartz space). Only Fréchet spaces with continuous norm are considered in this note.     

Positive Absolutely Summing Operators on the Köthe Spaces

In this paper we characterize the positive absolutely summing operators on the Köthe space E(X), with X a Banach lattice, extending a previous result. We prove that a composition operator of two positive absolutely summing operators is a positive absolutely summing operator. An interpolation result for the positive absolutely summing operators is obtained.     

Szegö Type Results Relative to a Sequence of Model Spaces

The classical Szegö theorem can be stated in terms of the sequence of model spaces ${(K_{z^N})_{N \in \mathbb{N}}}$ . In this article, we are interested in a generalization of the Szegö theorem in the case of the sequence ${(K_{B^N})_{N \in \mathbb{N}}}$ where B is a finite Blaschke product.     

Variants of the Maurey–Rosenthal Theorem for Quasi Köthe Function Spaces

The Maurey–Rosenthal theorem states that each bounded and linear operator T from a quasi normed space E into some L_p()(0) which satisfies a vector-valued norm inequality

Schauder Decompositions and the Grothendieck and Dunford-Pettis Properties in Köthe Echelon Spaces of Infinite Order

It is shown that every echelon space λ_∞(A), with A an arbitrary Köthe matrix, is a Grothendieck space with the Dunford-Pettis property. Since λ_∞(A) is Montel if and only if it coincides with λ₀(A), this identifies an extensive class of non-normable, non-Montel Fréchet spaces having these two properties. Even though the canonical unit vectors in λ_∞(A) fail to form an unconditional basis whenever λ_∞(A) ≠ λ₀(A), it is shown, nevertheless, that in this case λ_∞(A) still admits unconditional Schauder decompositions (provided it satisfies the density condition). This is in complete contrast to the Banach space setting, where Schauder decompositions never exist. Consequences for spectral measures are also given.     

On Weak Topology of Sequence Orlicz Spaces

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On a Property of Rearrangement Invariant Spaces whose Second Köthe Dual is Nonseparable

Mathematical Notes - We study the family of rearrangement invariant spaces E containing subspaces on which the E-norm is equivalent to the L1-norm and a certain geometric characteristic related to...     

The U—property of Orlicz Sequence Spaces

LetXbeaBanachspace,X'bethedualofX,S(X)={xeX:IIxII=l},B(X)={x6X:llxIlS1}betheunitsphereandunitballofX,respectively.ForxeX,let7xdenotethesetofsupportingfunctionalsfofS(X.)atx.Inl978,LauKa-singintroducedthefollowingnotiontostudytheChebyshevsubsetofX[1j:DefinitionABanachspaceXissaidtohaveU-propertyifforanyE>O,thereexists3>osuchthatSomeoftheresultsofU-propertyin[ljaresummarizedinthefollowing.Theorem(I)IfXhasU-property,thenXisuniformlynonSquare,inparticular,Xissuper-reflexive(infactr…     

Maluta＇s Coefficient of Musielak-Orlicz Sequence Spaces

In this paper, we give the formula of Maluta＇s coefficient for calculation, and don＇t add any conditions to the generating function Ф.     

Weakly~* Uniform Rotundity of Orlicz Sequence Spaces

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Besov Spaces for the Schrödinger Operator with Barrier Potential

Let H = ?d ²/dx ² + V be a Schrödinger operator on the real line, where \({V=c\chi_{[a,b]}}\) , c > 0. We define the Besov spaces for H by developing the associated Littlewood–Paley theory. This theory depends on the decay estimates of the spectral operator \({{\varphi}_j(H)}\) for the high and low energies. We also prove a Mihlin multiplier theorem on these spaces, including the L ^p boundedness result. Our approach has potential applications to other Schrödinger operators with short-range potentials.     

Weak Sequential Completeness of β-duals of Double Sequence Spaces

We consider dual pairs E,E ⁽⁾ of double sequence spaces E and E ⁽⁾, where E ⁽⁾ is the -dual space of E with respect to the -convergence of double sequences for = p (Pringsheim convergence), bp (bounded p-convergence) and r (regular convergence). Motivated by Boos, Fleming and Leiger [3], we introduce two oscillating properties (signed P_OSCP(k), k {1,2}) for a double sequence space E such that the signed P_OSCP(1) guarantees the (E ^(p), E)-sequential completeness of E ^(p), whereas the signed P_OSCP(2) implies the equalities E ^(r) = E ^(bp) = E ^(p) and the (E ⁽⁾, E)-sequentialcompleteness of E ⁽⁾ for = bp and r.     

On the Compactness of the Hypercomplex Commutator in Hölder Continuous Functions Spaces

This paper is devoted to the compactness of the hypercomplex commutator S _γ M _a ? M _a S _γ, where S _γ is the Cauchy singular integral operator (in the Douglis sense), a is a Hölder continuous hypercomplex function and M _a is the multiplication operator given by M _a f = a f. We extend a known compactness sufficient condition for the commutator of the Cauchy singular integral operator to the frame of the hypercomplex analysis, where γ is merely required to be an arbitrary regular closed Jordan curve.     

K—very Smooth Banach Spaces

We introduce the notion of K-very smoothness which is a generalization of very smoothness in Banach spaces. A necessary and sufficient condition for a Banach space to be K-very smooth is obtained. We also consider some relations between K-very smoothness and other geometrical notions.     

Embedding of Möbius Invariant Function Spaces into Tent Spaces

On the unit disk we introduce a new class of tent spaces \(T^q_{s,t}(\mu )\) for any positive Borel measure \(\mu \), consider a class of Möbius invariant spaces \(Z_p\) of analytic functions, and show that \(Z_p\) is contained in \(T^1_{p,1}\) if and only if \(\mu \) is a p-Carleson measure. This could be considered a continuation or variation of the work initiated by Xiao (Adv Math 217:2075–2088, 2008).     

Universal and comprehensive Gröbner bases of the classical determinantal ideal

Let A =(x _ij ), i =1,2,... ,k, j =1,2,... ,l, 1 ≤ k ≤ l, be a matrix of independent variables, G be the set of maximal minors of A, and I = (G) be the classical determinantal ideal. We show that G is a universal Gr?bner basis of I. Also, a sufficient condition for G to be a universal comprehensive Gr?bner basis is proved. Bibliography: 12 titles.     

A Survey on Frölicher Spaces

Abstract

This survey paper highlights a series of results in recent research on topology, geometry and categorical properties of spaces provided with a new structure in the mathematical literature, called Frölicher spaces. Without any fear of contradiction, these smooth spaces are stated to generalize the theory of differentiable manifolds. More precisely, the present study will give the state of research on this topic which historically links a fundamental theorem of calculus in so-called Boman's theorem (and its generalization) to abstract spaces, whether they are normable or not.