The Dirichlet Markov Ensemble

  • Authors:
  • Djalil Chafaï

  • Affiliations:
  • Laboratoire d'Analyse et de Mathématiques Appliquées (UMR CNRS 8050), Université Paris-Est Marne-la-Vallée, 5 boulevard Descartes, Champs-sur-Marne, F-77454, Cedex 2, France

  • Venue:
  • Journal of Multivariate Analysis
  • Year:
  • 2010

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Abstract

We equip the polytope of nxn Markov matrices with the normalized trace of the Lebesgue measure of R^n^^^2. This probability space provides random Markov matrices, with i.i.d. rows following the Dirichlet distribution of mean (1/n,...,1/n). We show that if M is such a random matrix, then the empirical distribution built from the singular values of nM tends as n-~ to a Wigner quarter-circle distribution. Some computer simulations reveal striking asymptotic spectral properties of such random matrices, still waiting for a rigorous mathematical analysis. In particular, we believe that with probability one, the empirical distribution of the complex spectrum of nM tends as n-~ to the uniform distribution on the unit disc of the complex plane, and that moreover, the spectral gap of M is of order 1-1/n when n is large.