Transport-entropy inequalities on locally acting groups of permutations

Paul-Marie Samson (1)

1 LAMA - Laboratoire d'Analyse et de Mathématiques Appliquées

Following Talagrand’s concentration results for permutations picked uniformly at random from a symmetric group [Tal95], Luczak and McDiarmid have generalized it to more general groups G of permutations which act suitably ‘locally’. Here we extend their results by setting transport-entropy inequalities on these permutations groups. Talagrand and Luczak-Mc-Diarmid concentra- tion properties are consequences of these inequalities. The results are also gen- eralised to a larger class of measures including Ewens distributions of arbitrary parameter θ on the symmetric group. By projection, we derive transport-entropy inequalities for the uniform law on the slice of the discrete hypercube and more generally for the multinomial law. These results are new examples, in discrete setting, of weak transport-entropy inequalities introduced in [GRST15], that con- tribute to a better understanding of the concentration properties of measures on permutations groups. One typical application is deviation bounds for the so- called configuration functions, such as the number of cycles of given lenght in the cycle decomposition of a random permutation.

Mots clés: Symmetric group; Random permutation; Transport inequalities; Concentration of measure; Slices of the discrete cube; Ewens distribution; Chinese restaurant process; Deviation’s inequalities for configuration functions

Domaines: Probabilités [math.PR]; Analyse fonctionnelle [math.FA]

Paul-Marie Samson. Transport-entropy inequalities on locally acting groups of permutations. Electronic Journal of Probability, 2017, Electron. J. Probab., 22 (62), ⟨10.1214/17-EJP54⟩. ⟨hal-01370491v3⟩