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The Peetre "plus-minus" interpolation spaces $\left\langle A_{0},A_{1}\right\rangle _{\theta}$ are defined variously via conditions about the unconditional convergence of certain Banach space valued series whose terms have coefficients…

Functional Analysis · Mathematics 2015-04-07 Michael Cwikel

In this article, we introduce a four-point analogue of Banach-type, Kannan-type, and Chatterjea-type contractions, and examine their properties. We establish sufficient conditions under which these mappings achieve fixed points in a…

Functional Analysis · Mathematics 2024-07-11 Anish Banerjee , Pratikshan Mondal , Lakshmi Kanta Dey

We characterise the class of those Banach spaces in which every convex combination of slices of the unit ball intersects the unit sphere as the class of those spaces in which every convex combination of slices of the unit ball contains two…

Functional Analysis · Mathematics 2019-01-24 Gines Lopez-Perez , Miguel Martin , Abraham Rueda Zoca

In this short note, we first consider some inequalities for comparison of some algebraic properties of two continuous algebra-multiplications on an arbitrary Banach space and then, as an application, we consider some very basic observations…

Functional Analysis · Mathematics 2019-07-24 Maysam Maysami Sadr

Multidimensional Consistency becomes more and more important in the theory of discrete integrable systems. Recently, we gave a classification of all 3D consistent 6-tuples of equations with the tetrahedron property, where several novel…

Exactly Solvable and Integrable Systems · Physics 2012-01-06 Raphael Boll

This is a write-up of a talk given at the CATMI meeting in Bergen in July 2023, and is an introduction to a category-theoretic perspective on metric spaces. A metric space is a set of points such that between each pair of points there is a…

Category Theory · Mathematics 2025-01-03 Simon Willerton

Multidimensional model describing the "cosmological" and/or spherically symmetric configuration with n+1 Einstein spaces in the theory with several scalar fields and forms is considered. When electro-magnetic composite p-brane ansatz is…

General Relativity and Quantum Cosmology · Physics 2007-05-23 V. D. Ivashchuk , V. N. Melnikov

Following Will Brian, we define a metric space $X$ to be $Banakh$ if all nonempty spheres of positive radius $r$ in $X$ have cardinality $2$ and diameter $2r$. Standard examples of Banakh spaces are subgroups of the real line. In this paper…

General Topology · Mathematics 2026-04-08 Taras Banakh

In this paper, we unify the theory of SSD spaces, part of the theory of strongly representable multifunctions, and the theory of the equivalence of various classes of maximally monotone multifunctions.

Functional Analysis · Mathematics 2008-11-03 Stephen Simons

In this paper we prove a plenty of new results concerning summabililty properties of multilinear mappings between Banach spaces, such as an extension of Littlewood's 4/3 Theorem. Among other features, it is shown that every continuous…

Functional Analysis · Mathematics 2008-10-14 Oscar Blasco , Geraldo Botelho , Daniel Pellegrino , Pilar Rueda

A Banach space $X$ has the $2$-summing property if the norm of every linear operator from $X$ to a Hilbert space is equal to the $2$-summing norm of the operator. Up to a point, the theory of spaces which have this property is independent…

Functional Analysis · Mathematics 2016-09-06 Alvaro Arias , Tadek Figiel , William B. Johnson , Gideon Schechtman

The objective of this manuscript is to introduce and develop the concept of a generalized $\theta$-parametric metric space-a novel extension that enriches the modern metric fixed point theory. We study of its fundamental properties,…

Optimization and Control · Mathematics 2025-10-02 Abhishikta Das , Hemanta Kalita , Mohammad Sajid , T. Bag

We give examples of real Banach spaces with exactly infinite countably many complex structures and with $\omega_1$ many complex structures.

Functional Analysis · Mathematics 2016-11-18 Wilson Cuellar-Carrera

In general Banach spaces, the metric projection map lacks the powerful properties it enjoys in Hilbert spaces. There are a few generalized projections that have been proposed in order to resolve many of the deficiencies of the metric…

Functional Analysis · Mathematics 2022-07-20 Akhtar A. Khan , Jinlu Li , Simeon Reich

Classes of Banach spaces that are finitely, strongly finitely or elementary equivalent are introduced. On sets of these classes topologies are defined in such a way that sets of defined classes become compact totally disconnected…

Functional Analysis · Mathematics 2007-05-23 Eugene Tokarev

We find necessary and sufficient conditions under which an arbitrary metric space $X$ has a unique pretangent space at the marked point $a\in X$. Key words: Metric spaces; Tangent spaces to metric spaces; Uniqueness of tangent metric…

Metric Geometry · Mathematics 2009-03-27 Oleksiy Dovgoshey , Fahreddin Abdullayev , Mehmet Kuchukaslan

In this paper, we investigate some properties of pluriharmonic mappings defined in the unit ball. First, we discuss some geometric univalence criteria on pluriharmonic mappings, and then establish a Landau-Bloch theorem for a class of…

Complex Variables · Mathematics 2014-02-11 Sh. Chen , S. Ponnusamy , X. Wang

We generalize the classical Multidimensional Scaling procedure to the setting of general metric measure spaces. We develop a related spectral theory for the generalized cMDS operator, which provides a more natural and rigorous mathematical…

Functional Analysis · Mathematics 2024-05-14 Sunhyuk Lim , Facundo Memoli

We single out and study a natural class of Banach spaces -- almost square Banach spaces. In an almost square space we can find, given a finite set $x_1,x_2,\ldots,x_N$ in the unit sphere, a unit vector $y$ such that $\|x_i-y\|$ is almost…

Functional Analysis · Mathematics 2015-08-25 Trond A. Abrahamsen , Johann Langemets , Vegard Lima

In the present article, we introduce a unified notion of multi-tupled fixed points and utilize the same to prove some existence and uniqueness unified multi-tupled fixed point theorems for Boyd-Wong type nonlinear contractions satisfying…

Functional Analysis · Mathematics 2016-01-12 Aftab Alam , Mohammad Imdad , Javid Ali