Über eine n-dimensionale Permutationspolynomgruppe.
Über Matrizen mit semidefinitem Realteil.
Über Ptolemäische Sätze.
Un problème d’approximation matricielle : quelle est la matrice bistochastique la plus proche d’une matrice donnée ?
Nous nous intéressons dans ce travail au problème d’approximation d’une matrice donnée par une matrice bistochastique. Des instances de ce problème peuvent apparaître dans différents domaines : en recherche opérationnelle dans un problème d’agrégation de préférence, en calcul de variations et optimisation de forme entre autres. Nous en proposons dans cet article une étude directe via le théorème de projection et une résolution numérique inspirée par la méthode de projections alternées de Boyle-Dykstra....
Unas notas sobre regularidad en matrices estocásticas.
Let P be a stochastic matrix. We give a necessary and sufficient condition for the existence of the limt -> ∞ ppt from which follows the classical regularity conditions. Another regularity condition based in the Banach point fix theorem is also given.
Unique prime factorization in a partial semigroup of matrix-polynomials
We establish a unique factorization result into irreducibel elements in the partial semigroup of 2 × 2-matrices with entries in K[x] whose determinant is equal to 1, where K is a field, and where multiplication is defined as the usual matrix-multiplication if the degrees of the factors add up. This investigation is motivated by a result on matrices of entire functions.
Unitary automorphisms of the space of Toeplitz-plus-Hankel matrices
Our motivation was a paper of 1991 indicating three special unitary matrices that map Hermitian Toeplitz matrices by similarity into real Toeplitz-plus-Hankel matrices. Generalizing this result, we give a complete description of unitary similarity automorphisms of the space of Toeplitz-plus-Hankel matrices.
Unitary completions of complex symmetric and skew symmetric matrices.
Universal and nonuniversal dynamical conductivity in small metallic grains: an ambivalent role of T-invariance at finite frequency.
Universal bounds for positive matrix semigroups
We show that any compact semigroup of positive n × n matrices is similar (via a positive diagonal similarity) to a semigroup bounded by √n. We give examples to show this bound is best possible. We also consider the effect of additional conditions on the semigroup and obtain improved bounds in some cases.
Universal factorization equalities over generalized quaternion algebras.
Universality for certain hermitian Wigner matrices under weak moment conditions
We study the universality of the local eigenvalue statistics of Gaussian divisible Hermitian Wigner matrices. These random matrices are obtained by adding an independent GUE matrix to an Hermitian random matrix with independent elements, a Wigner matrix. We prove that Tracy–Widom universality holds at the edge in this class of random matrices under the optimal moment condition that there is a uniform bound on the fourth moment of the matrix elements. Furthermore, we show that universality holds...
Universality in the random matrix spectra in the regime of weak non-hermiticity
Upper bound for the non-maximal eigenvalues of irreducible nonnegative matrices
We present a lower and an upper bound for the second smallest eigenvalue of Laplacian matrices in terms of the averaged minimal cut of weighted graphs. This is used to obtain an upper bound for the real parts of the non-maximal eigenvalues of irreducible nonnegative matrices. The result can be applied to Markov chains.
Upper bounds for the best normal approximation.
Upper bounds on certain functionals defined on groups of linear operators.