Necessary condition for the L2 boundedness of the Riesz transform on Heisenberg groups

Abstract

Let μ be a Radon measure on the n-th Heisenberg group Hn. In this note we prove that if the (2n+1)-dimensional (Heisenberg) Riesz transform on Hn is L2(μ)-bounded, and if μ(F)=0 for all Borel sets with dimH(F)2, then μ must have (2n+1)-polynomial growth. This is the Heisenberg counterpart of a result of Guy David from 1991.

Publication
Math. Proc. Cambridge Philos. Soc. 175, no. 2, 445-458.