Asymptotics of the determinant of discrete Laplacians on triangulated and quadrangulated surfaces

TL;DR

This paper derives the asymptotic behavior of the determinant of discrete Laplacians on surfaces made of triangles or squares, revealing universal and lattice-dependent constants, with implications for spectral geometry and mathematical physics.

Contribution

It provides a detailed asymptotic expansion for the determinant of discrete Laplacians on polygonal surfaces, including explicit constants and handling various boundary conditions.

Findings

Asymptotic formula involving surface area, boundary length, and logarithmic terms.

Explicit constants depending on lattice structure and bundle data.

Universal term interpreted as a zeta-regularized continuum Laplacian.

Abstract

Consider a surface $\Omega$ with a boundary obtained by gluing together a finite number of equilateral triangles, or squares, along their boundaries, equipped with a flat unitary vector bundle. Let $\Omega^{\delta}$ be the discretization of this surface by a bi-periodic lattice with enough symmetries, scaled to have mesh size $\delta$. We show that the logarithm of the product of non-zero eigenvalues of the discrete Laplacian acting on the sections of the bundle is asymptotic to \[ A|\Omega^{\delta}|+B|\partial\Omega^{\delta}|+C\log\delta+D+o(1). \] Here $A$ and $B$ are lattice-dependent constants; $C$ is an explicit constant depending on the bundle, the angles at conical singularities and at corners of the boundary, and $D$ is a sum of lattice-dependent contributions from singularities and a universal term that can be interpreted as a zeta-regularization of the continuum Laplacian on $\Omega$. We allow for Dirichlet or Neumann boundary conditions, or mixtures thereof. Our proof is based on an integral formula for the determinant in terms of theta function, and the functional Central limit theorem.