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We introduce and study a new class of nonlinear monotone operators acting in normal cones of real Banach spaces and possessing the property of strong concavity. We establish new constructive principles for the existence of nonzero fixed…

Functional Analysis · Mathematics 2026-04-27 Khachatur A. Khachatryan

Semigroups generated by topological operations such as closure, interior or boundary are considered. It is noted that some of these semigroups are in general finite and noncommutative. The problem is formulated whether they are always…

General Mathematics · Mathematics 2008-05-13 Elemer E Rosinger

The Kubo-Ando theory deals with connections for positive bounded operators. On the other hand, in various analysis related to von Neumann algebras it is impossible to avoid unbounded operators. In this article we try to extend a notion of…

Operator Algebras · Mathematics 2021-02-03 Fumio Hiai , Hideki Kosaki

In this short paper, we prove fixed point theorems for nonexpansive mappings whose domains are unbounded subsets of Banach spaces. These theorems are generalizations of Penot's result in [Proc. Amer. Math. Soc., 131 (2003), 2371--2377].

Functional Analysis · Mathematics 2007-05-23 Tomonari Suzuki

Let $A$ be a partial *-algebra endowed with a topology $\tau$ that makes it into a locally convex topological vector space $A[\tau]$. Then $A$ is called a topological partial *-algebra if it satisfies a number of conditions, which all…

Mathematical Physics · Physics 2009-04-07 J. -P. Antoine , F. Bagarello , C. Trapani

The paper is a survey of some results about Weil algebras applicable in differential geometry, especially in some classification questions on bundles of generalized velocities and contact elements. Mainly, a number of claims concerning a…

Differential Geometry · Mathematics 2010-11-11 Miroslav Kureš

In this paper we study analogues of amenability for topological groups in the context of definable structures. We prove fixed point theorems for such groups. More importantly, we propose definitions for definable actions and continuous…

Logic · Mathematics 2018-12-14 Alf Onshuus , Luis Carlos Suárez

The main purpose of this paper is to find the fixed point in such cases where existing literature remain silent. In this paper we introduce partial completeness, a new type of contraction and many other definitions. Using this approach the…

Functional Analysis · Mathematics 2018-03-23 Tawseef Rashid , Qamrul Haque Khan

We establish fixed-point theorems for Meir-Keeler-type contractions in b-metric spaces. While Lu et al. demonstrated via an explicit counterexample that classical Meir-Keeler contractions may fail to admit fixed points in this setting, we…

Metric Geometry · Mathematics 2025-06-12 Hassan Khandani

In this paper we present some fixed-figure theorems as a geometric approach to the fixed-point theory when the number of fixed points of a self-mapping is more than one. To do this, we modify the Jleli-Samet type contraction and define new…

Metric Geometry · Mathematics 2021-08-19 Hülya Atyimur , Nihal Taş

We obtain a fundamental inequality for a contraction with respect to a $C^*$-algebra valued metric space. As an application of this inequality a simple proof is given for the fixed point theorem in $C^*$-algebra valued metric space.

Functional Analysis · Mathematics 2017-08-15 Harsh Trivedi

In this paper the concept of unbounded Fredholm operators on Hilbert C*- modules over an arbitrary C*-algebra is discussed and the Atkinson theorem is generalized for bounded and unbounded Feredholm operators on Hilbert C*-modules over…

Operator Algebras · Mathematics 2015-06-26 Assadollah Niknam , Kamran Sharifi

In this paper we study a class of quadratic operators named by Volterra operators on infinite dimensional space. We prove that such operators have infinitely many fixed points and the set of Volterra operators forms a convex compact set. In…

Functional Analysis · Mathematics 2015-06-26 Farrukh Mukhamedov , Hasan Akin , Seyit Temir

A general fixed point theorem for isometries in terms of metric functionals is proved under the assumption of the existence of a conical bicombing. It is new even for isometries of Banach spaces as well as for non-locally compact…

Functional Analysis · Mathematics 2023-01-19 Anders Karlsson

We study possible noncommutative (operator algebra) variants of the classical Hoffman-Rossi theorem from the theory of function algebras. In particular we give a condition on the range of a contractive weak* continuous homomorphism defined…

Operator Algebras · Mathematics 2019-05-21 David P. Blecher , Luis C. Flores , Beate G. Zimmer

A general framework for obtaining certain types of contracted and centrally extended algebras is presented. The whole process relies on the existence of quadratic algebras, which appear in the context of boundary integrable models.

High Energy Physics - Theory · Physics 2014-11-20 Anastasia Doikou , Konstadinos Sfetsos

The aim of this paper is to prove the existence of common fixed points for a pair of weakly compatible selfmaps satisfying weakly contractive condition and property (E. A). In this context, first we modify Beg and Abbas theorem (\cite{Beg},…

Functional Analysis · Mathematics 2025-08-05 G. V. R. Babu , Alemayehu G. Negash

We extend the construction of generalized fixed point algebras to the setting of locally compact quantum groups - in the sense of Kustermans and Vaes - following the treatment of Marc Rieffel, Ruy Exel and Ralf Meyer in the group case. We…

Operator Algebras · Mathematics 2013-11-12 Alcides Buss

In this paper, for a given finitely generated algebra (an algebraic structure with arbitrary operations and no predicates) A we study finitely generated limit algebras of A, approaching them via model theory and algebraic geometry. Along…

Algebraic Geometry · Mathematics 2008-08-20 E. Daniyarova , A. Myasnikov , V. Remeslennikov

In this paper, the notion of $\mathbb{C}$-simulation function is introduced and the existence and uniqueness of common fixed points of two self-mappings satisfying contractive conditions in the setting of complex valued metric spaces via…

Functional Analysis · Mathematics 2019-05-10 Anuradha Gupta , Manu Rohilla