Laplacians on lattices
  We consider some lattices and look at discrete Laplacians on these lattices. In particular we look at solutions of the equation $\triangle(1)\phi = \triangle(2)Z$ where $\triangle(1)$ and $\triangle(2)$ are two such laplacians on the same lattice. We discuss solutions of this equation in some special cases. 
Wojtek Zakrzewski