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This paper establishes several new inequalities for the $A$-norm and $A$-numerical radius of operator sums in semi-Hilbertian spaces, significantly advancing the existing theory. We present two fundamental refinements of the generalized…

Functional Analysis · Mathematics 2025-07-09 M. H. M. Rashid

We study some properties convex functions fulfill. Among the conclusions we obtain from such result, we are able to prove some nontrivial inequalities among real numbers, and we give an improvement of the reverse triangle inequality in the…

We introduce a new type of mappings in metric space which are three-point analogue of the well-known Chatterjea type mappings, and call them generalized Chatterjea type mappings. It is shown that such mappings can be discontinuous as is the…

Metric Geometry · Mathematics 2025-05-27 Ovidiu Popescu , Cristina Maria Păcurar

It is generally known that in order to solve the split equality fixed-point problem (SEFPP), it is necessary to compute the norm of bounded and linear operators, which is a challenging task in real life, to address this issue, we studied…

General Mathematics · Mathematics 2024-04-01 Lawan Bulama Mohammed , Adem Kilicman

A set of lines in $\mathbb{R}^d$ passing through the origin is called equiangular if any two lines in the set form the same angle. We proved an alternative version of the three-point semidefinite constraints developed by Bachoc and…

Combinatorics · Mathematics 2022-03-14 Wei-Jiun Kao , Wei-Hsuan Yu

We established a fixed-point theorem for mapping satisfying a general contractive inequality of integral type depended an another function. This theorem substantially extend the theorem due to Branciari (2003) and Rhoades (2003)

Functional Analysis · Mathematics 2009-03-10 S. Moradi

This paper focuses on properties of \partial-biLipschitz mappings which were recently introduced by Bulter. We establish several characterizations for the class of \partial-biLipschitz mappings between domains in quasiconvex metric spaces.…

Complex Variables · Mathematics 2022-02-16 Tiantian Guan , Saminathan Ponnusamy , Qingshan Zhou

The aim of this paper is to investigate the equivalence conditions for uniform perfectness of quasi-metric spaces. We also obtain the invariant property of uniform perfectness under quasim\"obius maps in quasi-metric spaces. In the end, two…

Complex Variables · Mathematics 2019-03-05 Qingshan Zhou , Yaxiang Li , Ailing Xiao

In this paper, a new structure is defined on a topological space that equips the space with a concept of distance in order to do that firstly, a generalization of quasi-pseudo-metric space named R.O-metric space is introduced, and some of…

General Topology · Mathematics 2017-05-12 Hamid Shobeiri

We prove inequalities on non-integer powers of products of generalized matrices functions on the sum of positive semi-definite matrices. For example, for any real number $r \in \{1\} \cup [2, \infty)$, positive semi-definite matrices $A_i,\…

Functional Analysis · Mathematics 2016-09-01 Shaowu Huang , Chi-Kwong Li , Yiu-Tung Poon , Qing-Wen Wang

The main aim of this note, which can be viewed as a certain addendum to the paper \cite{2019}, is to propose several generalized inequalities for the ratio functions of trigonometric and hyperbolic functions. We basically follow the…

General Mathematics · Mathematics 2024-04-08 Marko Kostić , Yogesh J. Bagul , Christophe Chesneau

Certain triangle inequalities involving the circumradius, inradius, and side lengths of a triangle are generalized to spherical and hyperbolic geometry. Examples include strengthenings of Euler's inequality, $R\geq2r$. An extension of…

History and Overview · Mathematics 2018-05-30 Karina Cho , Jacob Naranjo

We introduce a new class of quasi-Banach spaces as an extension of the classical Grand Lebesgue Spaces for small values of the parameter, and we investigate some its properties, in particular, completeness, fundamental function, operators…

Functional Analysis · Mathematics 2020-08-07 Maria Rosaria Formica , Eugeny Ostrovsky , Leonid Sirota

In this work, a generalization of Chebyshev functional is presented. New inequalities of Gruss type via Pompeiu's mean value theorem are established. Improvements of some old inequalities are proved. A generalization of pre-Gruss inequality…

Classical Analysis and ODEs · Mathematics 2019-05-24 Mohammad W. Alomari

A study is made of linear isometries on Fr\'echet spaces for which the metric is given in terms of a sequence of seminorms. This establishes sufficient conditions on the growth of the function that defines the metric in terms of the…

Functional Analysis · Mathematics 2025-06-23 Isabelle Chalendar , Lucas Oger , Jonathan R. Partington

Harmonic, Geometric, Arithmetic, Heronian and Contraharmonic means have been studied by many mathematicians. In 2003, H. Evens studied these means from geometrical point of view and established some of the inequalities between them in using…

Other Statistics · Statistics 2020-01-06 Fariba Khoshnasib-Zeinabad , Mohammadhossein Mehrabi

Chen and Chv\'atal conjectured in 2008 that in any finite metric space either there is a line containing all the points - a universal line -, or the number of lines is at least the number of points. This is a generalization of a classical…

Combinatorics · Mathematics 2024-05-30 Guillermo Gamboa Quintero , Martín Matamala , Juan Pablo Peña

In 1980 P. Tukia and J. V\"{a}is\"{a}l\"{a} in seminal paper [P. Tukia and J. V\"ais\"al\"a, Quasisymmetric embeddings of metric spaces, Ann. Acad. Sci. Fenn., Ser. A I, Math. 5, 97--114 (1980)] extended a concept of quasisymmetric mapping…

General Topology · Mathematics 2025-01-07 Evgeniy Petrov , Ruslan Salimov

A branch of generalizations of the Banach Fixed Point Theorem replaces contractivity by a weaker but still effective property. The aim of the present note is to extend the contraction principle in this spirit for such complete semimetric…

Functional Analysis · Mathematics 2017-06-29 Mihály Bessenyei , Zsolt Páles

We describe a very general abstract form of sieve based on a large sieve inequality which generalizes both the classical sieve inequality of Montgomery (and its higher-dimensional variants), and our recent sieve for Frobenius over function…

Number Theory · Mathematics 2007-05-23 Emmanuel Kowalski