Émergence du concept de rang dans l'étude des systèmes d'équations linéaires
Analytic continuation and domains of holomorphy for solution to the complex Laplace and Dirac equations in are studied. First, geometric description of envelopes of holomorphy over domains in is given. In more general case, solutions can be continued by integral formulas using values on a real dimensional cycle in . Sufficient conditions for this being possible are formulated.
A complex square matrix A is called an orthogonal projector if A 2 = A = A*, where A* denotes the conjugate transpose of A. In this paper, we give a comprehensive investigation to matrix expressions consisting of orthogonal projectors and their properties through ranks of matrices. We first collect some well-known rank formulas for orthogonal projectors and their operations, and then establish various new rank formulas for matrix expressions composed by orthogonal projectors. As applications, we...
In this paper we give necessary and sufficient conditions for the equality case in Wielandt’s eigenvalue inequality.
We present a survey of results on word equations in simple groups, as well as their analogues and generalizations, which were obtained over the past decade using various methods: group-theoretic and coming from algebraic and arithmetic geometry, number theory, dynamical systems and computer algebra. Our focus is on interrelations of these machineries which led to numerous spectacular achievements, including solutions of several long-standing problems.