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We introduce the notion of approximate smoothness in a normed linear space. We characterize this property and show the connections between smoothness and approximate smoothness for some spaces. As an application, we consider in particular…

Functional Analysis · Mathematics 2022-11-08 Jacek Chmieliński , Divya Khurana , Debmalya Sain

We study the concepts of Birkhoff--James orthogonality and parallelism in Hilbert space operators, induced by the operator radius norm $w_{\rho}(\cdot)$. In particular, we completely characterize Birkhoff--James orthogonality and…

Functional Analysis · Mathematics 2024-05-14 Fuad Kittaneh , Ali Zamani

We obtain a necessary and sufficient condition for a matrix $A$ to be Birkhoff-James orthogonal to any subspace $\mathscr W$ of $\mathbb M_n(\mathbb C)$. Using this we obtain an expression for the distance of $A$ from any unital $C^*$…

Functional Analysis · Mathematics 2017-05-23 Priyanka Grover

We study Birkhoff-James orthogonality and its local symmetry in some sequence spaces namely $\ell_p,$ for $1\leq p\leq\infty$, $p\neq2$, $c$, $c_0$ and $c_{00}$. Using the characterization of the local symmetry of Birkhoff-James…

Functional Analysis · Mathematics 2022-05-25 Babhrubahan Bose , Saikat Roy , Debmalya Sain

Real smooth three-dimensional or higher Banach spaces are isomorphic with respect to the nonlinear structure of Birkhoff-James orthogonality if and only if they are isometrically isomorphic. Moreover, using smooth Radon planes and…

Functional Analysis · Mathematics 2021-08-03 Ryotaro Tanaka

We explore Birkhoff-James orthogonality of two elements in a complex Banach space by using the directional approach. Our investigation illustrates the geometric distinctions between a smooth point and a non-smooth point in a complex Banach…

Functional Analysis · Mathematics 2021-09-28 Saikat Roy , Satya Bagchi , Debmalya Sain

We characterize Birkhoff-James orthogonality of continuous vector-valued functions on a compact topological space. As an application of our investigation, Birkhoff-James orthogonality of real bilinear forms are studied. This allows us to…

Functional Analysis · Mathematics 2024-07-19 Saikat Roy , Tanusri Senapati , Debmalya Sain

The orthogonality properties of certain subspaces associated with bivariate Bernstein-Szeg\H{o} measures are considered. It is shown that these spaces satisfy more orthogonality relations than expected from the relations that define them.…

Complex Variables · Mathematics 2012-09-13 Jeffrey S. Geronimo , Plamen Iliev , Greg Knese

In this paper we study Birkhoff-James Orthogonality for biadjoints of operators. We partly solve the problem, if an operator is orthogonal to the space of operators valued in a subspace, when the is the norm of biadjoint is attained at a…

Functional Analysis · Mathematics 2022-12-13 Taduri Srinivasa Siva Rama Krishna Rao

We study the problem of calculating noncommutative distances on graphs, using techniques from linear algebra, specifically, Birkhoff-James orthogonality. A complete characterization of the solutions is obtained in the case when the…

Operator Algebras · Mathematics 2024-09-09 Pierre Clare , Chi-Kwong Li , Edward Poon , Eric Swartz

We study the Gateaux differentiability in the Banach space of meromorphic functions and obtain a complete characterization of the same, by using Birkhoff-James orthogonality techniques. We introduce the concept of extended orthogonality…

Complex Variables · Mathematics 2024-11-01 Sanjay Mallick , Debmalya Sain

This paper explores the concept of approximate Birkhoff-James orthogonality in the context of operators on semi-Hilbert spaces. These spaces are generated by positive semi-definite sesquilinear forms. We delve into the fundamental…

Functional Analysis · Mathematics 2023-12-19 Cristian Conde , Kais Feki

In this paper we characterize Birkhoff-James orthogonality of linear operators defined on a finite dimensional real Banach space $ \mathbb{X}. $ We also explore the symmetry of Birkhoff-James orthogonality of linear operators defined on $…

Functional Analysis · Mathematics 2016-07-29 Debmalya Sain

Motivated by the famous Blanco-Koldobsky-Turn\v{s}ek characterization of isometries, we study the \textit{approximate preservation of Birkhoff-James orthogonality by a linear operator between Banach spaces}. In particular, we investigate…

Functional Analysis · Mathematics 2025-01-22 Kalidas Mandal , Jayanta Manna , Kallol Paul , Debmalya Sain

Our principal aim is to illustrate that the concept Birkhoff-James orthogonality can be applied effectively to obtain a unified approach to a large family of optimization problems in Banach spaces. We study such optimization problems from…

Functional Analysis · Mathematics 2025-01-22 Kallol Paul , Saikat Roy , Debmalya Sain , Shamim Sohel

Motivated by the work of Baronti et al. [J. Math. Anal. Appl. 252(2000) 124-146], where they defined the supremum of an arithmetic mean of the side lengths of a triangle, summing antipodal points on the unit sphere, we introduce a new…

Functional Analysis · Mathematics 2026-01-01 Kallal Pal , Sumit Chandok

We study the relationship between the point-wise symmetry of Birkhoff-James orthogonality and the geometry of the space of operators $\mathbb{B}(\ell_\infty^n,\ell_1^m)$. We show that any non-zero left-symmetric point in this space is a…

Functional Analysis · Mathematics 2022-11-17 Babhrubahan Bose

In this paper we explore the properties of a bounded linear operator defined on a Banach space, in light of operator norm attainment. Using Birkhoff-James orthogonality techniques, we give a necessary condition for a bounded linear operator…

Functional Analysis · Mathematics 2016-08-03 Debmalya Sain

We study approximate Birkhoff-James orthogonality of bounded linear operators defined between normed linear spaces $\mathbb{X}$ and $\mathbb{Y}.$ As an application of the results obtained, we characterize smoothness of a bounded linear…

Functional Analysis · Mathematics 2024-08-13 Arpita Mal , Kallol Paul , T. S. S. R. K. Rao , Debmalya Sain

We combine functional analytic and geometric viewpoints on approximate Birkhoff and isosceles orthogonality in generalized Minkowski spaces which are finite-dimensional vector spaces equipped with a gauge. This is the first approach to…

Metric Geometry · Mathematics 2017-07-18 Thomas Jahn