Lattice Points Close to the Heisenberg Spheres

Abstract

We study a lattice point-counting problem for spheres arising from the Heisenberg groups. In particular, we prove an upper bound on the number of points on and near large dilates of the unit spheres generated by the anisotropic norms $$\Vert (z,t)\Vert _\alpha = ( \left| z\right| ^\alpha + \left| t\right| ^{\alpha /2})^{1/\alpha }$$ for $$\alpha \ge 2$$ . As a first step, we reduce our counting problem to one of bounding an energy integral. The primary new challenges that arise are the presence of vanishing curvature and nonisotropic dilations. In the process, we establish bounds on the Fourier transform of the surface measures arising from these norms. Further, we utilize the techniques developed here to estimate the number of lattice points in the intersection of two such surfaces.