Quantum Pick's Theorem in two dimensions

Abstract

Consider an $n$-dimensional sum of the form $S_k=\sum{q^{f({\bf z})}}$ over lattice points ${\bf z}$ which lie in $K{\mathcal P}$, the $K$ scaling of an $n$-dimensional rational polytope $\mathcal P$. We formulate a conjecture on the structure of $S_K$ considered for $K$ prime, as a power series in $h=q-1$ modulo the $K^{th}$ cyclotomic polynomial, and in particular the existence of a decomposition in powers of the Gauss sum $\mathbb G$, up to the $n^{th}$, whose coefficients are almost independent of $K$, where the leading coefficient is related to the volume of $\mathcal P$ and the coefficient of ${\mathbb G}^r$ has contributions from the codimension $r$ skeleton of $\mathcal P$. The conjecture is proved for $n=1,2$.