paper

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

arXiv:2007.08941 · doi:10.1007/s00220-022-04437-3

Abstract

Consider a surface 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 be the discretization of this surface by a bi-periodic lattice with enough symmetries, scaled to have mesh size . 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 \[ A|Ω^δ|+B|\partialΩ^δ|+C\logδ+D+o(1). \] Here and are lattice-dependent constants; is an explicit constant depending on the bundle, the angles at conical singularities and at corners of the boundary, and 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 . 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.

34 pages. Version 2: added a discussion of self-adjoint extensions of the Laplacian, the associated Dirichlet forms and semi-groups in the continuum. The explicit values of the constant B ("boundary tension") computed for several lattices

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