Hypercontractivity for log-subharmonic functions
Résumé
We prove strong hypercontractivity (SHC) inequalities for logarithmically subharmonic functions on R n and different classes of measures: Gaussian measures on R n , symmetric Bernoulli and symmetric uniform probability measures on R , as well as their convolutions. Surprisingly, a slightly weaker strong hypercontractivity property holds for any symmetric measure on R . A log-Sobolev inequality (LSI) is deduced from the (SHC) for compactly supported measures on R n , still for log-subharmonic functions. An analogous (LSI) is proved for Gaussian measures on R n and for other measures for which we know the (SHC) holds. Our log-Sobolev inequality holds in the log-subharmonic category with a constant smaller than the one for Gaussian measure in the classical context.