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This article introduces PnCP, a MATLAB toolbox for constructing positive maps which are not completely positive. We survey optimization and sum of squares relaxation techniques to find the most numerically efficient methods for this…

Optimization and Control · Mathematics 2020-01-07 Abhishek Bhardwaj

We develop new, easily computable exponential decay bounds for inverses of banded matrices, based on the quasiseparable representation of Green matrices. The bounds rely on a diagonal dominance hypothesis and do not require explicit…

Numerical Analysis · Mathematics 2025-11-05 Paola Boito , Yuli Eidelman

We establish new analytic and numerical results on a general class of rational operator Nevanlinna functions that arise e.g. in modelling photonic crystals. The capability of these dielectric nano-structured materials to control the flow of…

Mathematical Physics · Physics 2015-07-24 Christian Engström , Heinz Langer , Christiane Tretter

We study properties of eigenvalues of a matrix associated with a randomly chosen partial automorphism of a regular rooted tree. We show that asymptotically, as the numbers of levels goes to infinity, the fraction of non-zero eigenvalues…

Group Theory · Mathematics 2020-06-30 Eugenia Kochubinska

We prove that the matrix of capacitance in electrostatics is a positive-singular matrix with a non-degenerate null eigenvalue. We explore the physical implications of this fact, and study the physical meaning of the eigenvalue problem for…

Classical Physics · Physics 2015-01-20 Rodolfo A. Diaz , William J. Herrera

In this short note, we present a novel method for computing exact lower and upper bounds of eigenvalues of a symmetric tridiagonal interval matrix. Compared to the known methods, our approach is fast, simple to present and to implement, and…

Numerical Analysis · Computer Science 2018-07-10 Milan Hladík

We present an efficient algorithm for the application of sequences of planar rotations to a matrix. Applying such sequences efficiently is important in many numerical linear algebra algorithms for eigenvalues. Our algorithm is novel in…

Performance · Computer Science 2024-12-04 Thijs Steel , Julien Langou

The eigenvalues of the Laplacian matrix for a class of directed graphs with both positive and negative weights are studied. First, a class of directed signed graphs is investigated in which one pair of nodes (either connected or not) is…

Optimization and Control · Mathematics 2017-05-15 Saeed Ahmadizadeh , Iman Shames , Samuel Martin , Dragan Nesic

Recently, the eigenvalue problems formulated with symmetric positive definite bilinear forms have been well investigated with the aim of explicit bounds for the eigenvalues. In this paper, the existing theorems for bounding eigenvalues are…

Numerical Analysis · Mathematics 2019-04-25 Xuefeng Liu

We study the spectral properties of certain non-self-adjoint matrices associated with large directed graphs. Asymptotically the eigenvalues converge to certain curves, apart from a finite number that have limits not on these curves.

Spectral Theory · Mathematics 2008-02-12 E. B. Davies , Paul A. Incani

In this paper, we obtain a sharp upper bound for the spectral radius of a nonnegative matrix. This result is used to present upper bounds for the adjacency spectral radius, the Laplacian spectral radius, the signless Laplacian spectral…

Combinatorics · Mathematics 2016-07-21 Lihua You , Yujie Shu , Xiao-Dong Zhang

We completely characterize the conditions under which a complex unitary number is an eigenvalue of the non-backtracking matrix of an undirected graph. Further, we provide a closed formula to compute its geometric multiplicity and describe…

Combinatorics · Mathematics 2026-01-05 Leo Torres

We show that randomly choosing the matrices in a completely positive map from the unitary group gives a quantum expander. We consider Hermitian and non-Hermitian cases, and we provide asymptotically tight bounds in the Hermitian case on the…

Quantum Physics · Physics 2009-11-13 M. B. Hastings

For a self--adjoint Laplace operator on a finite, not necessarily compact, metric graph lower and upper bounds on each of the negative eigenvalues are derived. For compact finite metric graphs Poincar\'{e} type inequalities are given.

Spectral Theory · Mathematics 2021-03-29 Amru Hussein

For a rational function of several variables with nonnegative imaginary part on the upper poly-half-plane, the matrix representations are obtained.

Complex Variables · Mathematics 2021-11-30 M. F. Bessmertnyi

We survey some of the known results on eigenvalues of Cayley graphs and their applications, together with related results on eigenvalues of Cayley digraphs and generalizations of Cayley graphs.

Combinatorics · Mathematics 2022-04-25 Xiaogang Liu , Sanming Zhou

It is critical to understand the properties of spatial correlation matrices in massive multiple-input multiple-output (MIMO) systems. We derive new bounds on the extreme eigenvalues of a spatial correlation matrix that is characterized by…

Information Theory · Computer Science 2014-06-23 Junil Choi , David J. Love

Nonlinear eigenvalue problems with eigenvector nonlinearities (NEPv) are algebraic eigenvalue problems whose matrix depends on the eigenvector. Applications range from computational quantum mechanics to machine learning. Due to its…

Numerical Analysis · Mathematics 2025-10-06 Victor Janssens , Karl Meerbergen , Wim Michiels

By studying the minimum resources required to perform a unitary transformation, families of metrics and pseudo-metrics on unitary matrices that are closely related to a recently reported quantum speed limit by the author are found.…

Quantum Physics · Physics 2011-07-07 H. F. Chau

We give a specific method to solve with quadratic complexity the linear systems arising in known algorithms to deal with the sign determination problem. In particular, this enable us to improve the complexity bound for sign determination in…

Algebraic Geometry · Mathematics 2009-12-01 Daniel Perrucci