On singular integrals with non-negative kernels in the Heisenberg group

Vasileios Chousionis, Sean Li, Lingxiao Zhang

In this paper we revisit nonnegative kernels in the first Heisenberg group $\He$, and in particular we further study the family $$K_α(x,y,z)= \frac{|z|^{α/2}}{\|(x,y,z)\|_{H}^{α+1}…