Title: Hypercontractivity for free products.
Author(s): Marius Junge, Carlos Palazuelos, Javier Parcet, Mathilde Perrin, Éric Ricard.
Source: Annales scientifiques de l’ENS 48, fascicule 4 (2015), 861-889
Date of publication: 2015.
Abstract: In this paper, we obtain optimal time hypercontractivity bounds for the free product extension of the Ornstein-Uhlenbecksemigroup acting on the Clifford algebra. Our approach is based on a central limit theorem for free products of spin matrix algebras with mixed commutation/anticommutation relations. With another use of Speicher’s central limit theorem, we can also obtain the same bounds for free products of q-deformed von Neumann algebras interpolating between the fermonic and bosonic frameworks. This generalizes the work of Nelson, Gross, Carlen/Lieb and Biane. Our main application yields hypercontractivity bounds for the free Poisson semigroup acting on the group algebra of the free group Fn, uniformly in the number of generators.