Subgaussian 1-cocycles on discrete groups

Abstract

We prove the $L_p$ Poincaré inequalities with constant $C\sqrt{p}$ for $1$-cocycles on countable discrete groups under Bakry--Emery's $Γ_2$-criterion. These inequalities determine an analogue of subgaussian behavior for 1-cocycles. Our theorem improves some of our previous results in this direction, and in particular implies Efraim and Lust-Piquard's Poincaré type inequalities for the Walsh system. The key new ingredient in our proof is a decoupling argument. As complementary results, we also show that the spectral gap inequality implies the $L_p$ Poincaré inequalities with constant $C{p}$ under some conditions in the noncommutative setting. New examples which satisfy the $Γ_2$-criterion are provided as well.

29 pages