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Let $A$ be a positive operator on a complex Hilbert space $\mathcal{H}.$ We present inequalities concerning upper and lower bounds for $A$-numerical radius of operators, which improve on and generalize the existing ones, studied recently in…

Functional Analysis · Mathematics 2024-08-13 Pintu Bhunia , Kallol Paul , Raj Kumar Nayak

We provide a simple way to add, multiply, invert, and take traces and norms of algebraic integers of a number field using integral matrices. With formulas for the integral bases of the ring of integers of at least a significant proportion…

Number Theory · Mathematics 2018-09-26 Samuel A. Hambleton

On Hadamard manifolds, the radial fields, which are the negative gradients of the Busemann functions, can be used to designate a canonical sense of direction. This could have many potential applications to Hadamard manifold-valued data, for…

Differential Geometry · Mathematics 2026-01-05 Ha-Young Shin

The invariant polytope algorithm was a breakthrough in the joint spectral radius computation, allowing to find the exact value of the joint spectral radius for most matrix families~\cite{GP2013,GP2016}. This algorithm found many…

Numerical Analysis · Mathematics 2025-05-16 Thomas Mejstrik

This work explores fundamental modeling and algorithmic issues arising in the well-established MapReduce framework. First, we formally specify a computational model for MapReduce which captures the functional flavor of the paradigm by…

Data Structures and Algorithms · Computer Science 2013-06-13 Andrea Pietracaprina , Geppino Pucci , Matteo Riondato , Francesco Silvestri , Eli Upfal

We investigate the turnaround radius in the spherical collapse model, both in General Relativity and in modified gravity, in particular $f(R)$ scenarios. The phases of spherical collapse are marked by the density contrast in the instant of…

Cosmology and Nongalactic Astrophysics · Physics 2018-09-19 Rafael C. C. Lopes , Rodrigo Voivodic , Luis Raul Abramo , Laerte Sodré

Any associative bilinear multiplication on the set of n-by-n matrices over some field of characteristic not two, that makes the same vectors orthogonal and has the same trace as ordinary matrix multiplication, must be ordinary matrix…

Rings and Algebras · Mathematics 2023-04-21 Chris Heunen , Dominic Horsman

Mixed radix bases in numeration is a very old notion but it is rarely studied on its own or in relation with concrete problems related to number theory. Starting from the natural question of the conversion of a basis to another for integers…

Mathematical Physics · Physics 2025-03-28 Damien Simon

We develop upper and lower bounds for the numerical radius of $2\times 2$ off-diagonal operator matrices, which generalize and improve on the existing ones. We also show that if $A$ is a bounded linear operator on a complex Hilbert space…

Functional Analysis · Mathematics 2021-10-07 Pintu Bhunia , Kallol Paul

We obtain upper bounds for the numerical radius of a product of Hilbert space operators which improve on the existing upper bounds. We generalize the numerical radius inequalities of $n\times n$ operator matrices by using non-negative…

Functional Analysis · Mathematics 2024-08-13 Pintu Bhunia , Kallol Paul

We define a special matrix multiplication among a special subset of $2N\x 2N$ matrices, and study the resulting (non-associative) algebras and their subalgebras. We derive the conditions under which these algebras become alternative…

High Energy Physics - Theory · Physics 2009-10-31 J Daboul , R Delbourgo

We revisit the concept of turnaround radius in cosmology, in the context of modified gravity. While preliminary analyses were limited to scalar-tensor/$F(R)$ gravity, we extend the definition and the study of this quantity to a much broader…

General Relativity and Quantum Cosmology · Physics 2018-07-11 Shin'ichi Nojiri , Sergei D. Odintsov , Valerio Faraoni

In this paper, we give upper and lower bounds for the spectral radius of a nonnegative irreducible matrix and characterize the equality cases. These bounds theoretically improve and generalize some known results of Duan et al.[X. Duan, B.…

Combinatorics · Mathematics 2013-10-22 Shu-Yu Cui , Gui-Xian Tian

In this article the quantized matrix algebras as in the title have been studied at a root of unity. A full classification of simple modules over such quantized matrix algebras of rank $2$ along with a class of finite dimensional…

Quantum Algebra · Mathematics 2022-06-22 Snehashis Mukherjee , Sanu Bera

In this survey paper we study parametric versions of writing a matrix in $SL_n (\mathbb{C})$ as a product of lower and upper unitriangular matrices in interchanging order as well as generalizations to other classical groups. We give an…

Complex Variables · Mathematics 2026-01-06 Gaofeng Huang , Frank Kutzschebauch

The question of matrix similarity is a classical one in linear algebra. For a field $\mathbb{F}$ and some positive integer $n \in \mathbb{N}$, one may consider the following problems: 1. Given two matrices $A, B \in \mathrm{GL}(n,…

Rings and Algebras · Mathematics 2026-05-07 Alia Bonnet

This article has two interpenetrating motifs. One is an exposition of some major ideas and techniques behind the use of block matrices, and especially their positivity properties. This is done by focussing on one major problem:…

Functional Analysis · Mathematics 2023-08-01 Rajendra Bhatia , Tanvi Jain

By [R. Bautista, P. Gabriel, A.V Roiter., L. Salmeron, Representation-finite algebras and multiplicative basis. Invent. Math. 81 (1985) 217-285.], a finite-dimensional algebra having finitely many isoclasses of indecomposable…

Representation Theory · Mathematics 2007-11-17 Andrej V. Roiter , Vladimir V. Sergeichuk

In this paper, with the help of trinomial coefficients we study some arithmetic properties of certain determiants involving reciprocals of binary quadratic forms over finite fields.

Number Theory · Mathematics 2024-07-25 Yue-Feng She , Hai-Liang Wu

The main contribution of this paper is a new improved variant of the laser method for designing matrix multiplication algorithms. Building upon the recent techniques of [Duan, Wu, Zhou, FOCS 2023], the new method introduces several new…

Data Structures and Algorithms · Computer Science 2023-11-07 Virginia Vassilevska Williams , Yinzhan Xu , Zixuan Xu , Renfei Zhou