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For an exact quantitative description of spectral properties in the theory of synchrotron radiation, the concept of effective spectral width is introduced. In the classical theory, numeric calculations of effective spectral width (using an…

Classical Physics · Physics 2017-06-28 V. G. Bagrov , D. M. Gitman , A. D. Levin , A. S. Loginov , A. D. Saprykin

We determine the structure of linear maps on complex (real) square matrices sending unitary (orthogonal) matrices to multiples of unitary (orthogonal) matrices. The result is used to determine the linear preservers of matrix pairs…

Functional Analysis · Mathematics 2025-10-08 Bojan Kuzma , Chi-Kwong Li , Edward Poon

We characterize real and complex functions which, when applied entrywise to square matrices, yield a positive definite matrix if and only if the original matrix is positive definite. We refer to these transformations as sign preservers.…

Classical Analysis and ODEs · Mathematics 2026-05-08 Dominique Guillot , Himanshu Gupta , Prateek Kumar Vishwakarma , Chi Hoi Yip

The possible spatial transformation properties of tetrons are discussed.

High Energy Physics - Phenomenology · Physics 2009-02-11 Bodo Lampe

In this paper we determine those bijective maps of the set of all positive definite $n\times n$ complex matrices which preserve a given Bregman divergence corresponding to a differentiable convex function that satisfies certain conditions.…

Functional Analysis · Mathematics 2016-02-25 Lajos Molnár , József Pitrik , Dániel Virosztek

The matrix inversion is an interesting topic in algebra mathematics. However, to determine an inverse matrix from a given matrix is required many computation tools and time resource if the size of matrix is huge. In this paper, we have…

Discrete Mathematics · Computer Science 2017-08-28 Thuan Nguyen

The partial transpose of a block matrix M is the matrix obtained by transposing the blocks of M independently. We approach the notion of partial transpose from a combinatorial point of view. In this perspective, we solve some basic…

Combinatorics · Mathematics 2008-03-22 Qing-Hu Hou , Toufik Mansour , Simone Severini

We suggest a way to manipulate electromagnetic wave by introducing a rotation mapping of coordinates that can be realized by a specific transformation of permittivity and permeability of a shell surrounding an enclosed domain. Inside the…

Optics · Physics 2007-06-12 Huanyang Chen , C. T. Chan

The transition-matrix ($T$-matrix) approach provides a general formalism to study scattering problems in various areas of physics, including acoustics (scalar fields) and electromagnetics (vector fields), and is related to the theory of the…

Optics · Physics 2016-02-08 Eric C. Le Ru , Walter R. C. Somerville , Baptiste Auguié

The rational Landen transformation is a map on the space of coefficients of a rational integrand that preserves the value of the integral. We provide a family of these transformations that apply to rational integrands on the whole line.…

Classical Analysis and ODEs · Mathematics 2009-11-13 Dante Manna , Victor H. Moll

We revisit the relative perturbation theory for invariant subspaces of positive definite matrix pairs. As a prototype model problem for our results we consider parameter dependent families of eigenvalue problems. We show that new estimates…

Numerical Analysis · Mathematics 2010-11-22 Luka Grubišić , Ninoslav Truhar , Krešimir Veselić

The aim of this article is to present a brief overview of spectral perturbation theory for matrices, bounded linear operators and holomorphic operator-valued functions. We focus on bounds for perturbed eigenvalues, eigenvectors and…

Spectral Theory · Mathematics 2025-12-09 Rafikul Alam

We survey recent developments in the theory and applications of the broken ray transforms. Furthermore, we discuss some open problems.

Differential Geometry · Mathematics 2025-08-12 Shubham R. Jathar , Jesse Railo

We describe a general approach for computing generators for elimination ideals associated with matrix and hypermatrix spectral decomposition constraints. We derive from these generators iterative procedures for approximating the spectral…

Spectral Theory · Mathematics 2015-03-24 Edinah K. Gnang

We prove that all injective maps on positive complex matrices which preserve order and shrink spectrum are implemented by unitary or antiunitary conjugations. We show by counterexamples that all assumptions are indispensable. The result…

Functional Analysis · Mathematics 2022-04-26 Mateo Tomašević

Convenient parameterizations of matrices in terms of vectors transform (certain classes of) matrix equations into covariant (hence rotation-invariant) vector equations. Certain recently introduced such parameterizations are tersely…

Exactly Solvable and Integrable Systems · Physics 2009-11-10 M. Bruschi , F. Calogero

The joint spectral radius of a set of matrices is a measure of the maximal asymptotic growth rate that can be obtained by forming long products of matrices taken from the set. This quantity appears in a number of application contexts but is…

Dynamical Systems · Mathematics 2007-05-23 Vincent Blondel , Yurii Nesterov

Transformation optics is a powerful tool to design various novel devices, such as invisibility cloak. Fantastic effects from this technique are usually accompanied with singular mappings, resulting in challenging implementations and narrow…

Optics · Physics 2016-02-08 M. M. Sadeghi , Sucheng Li , Lin Xu , Bo Hou , Huanyang Chen

A path integral formulation is developed to study the spectrum of radiation from a perfectly reflecting (conducting) surface. It allows us to study arbitrary deformations in space and time. The spectrum is calculated to second order in the…

Quantum Physics · Physics 2009-10-31 Faez Miri , Ramin Golestanian

The numerical radius of a matrix is a scalar quantity that has many applications in the study of matrix analysis. Due to the difficulty in computing the numerical radius, inequalities bounding it have received a considerable attention in…

Functional Analysis · Mathematics 2020-07-20 Yassine Bedrani , Fuad Kittaneh , Mohammed Sababheh