Length orthospectrum of convex bodies on flat tori

In analogy with the study of Pollicott-Ruelle resonances on negatively curved manifolds, we define anisotropic Sobolev spaces that are well-adapted to the analysis of the geodesic vector field associated with any translation invariant Finsler metric on the torus ${\mathbb{T}}^d$. Among several applications of this functional point of view, we study properties of geodesics that are orthogonal to two convex subsets of ${\mathbb{T}}^d$ (i.e. projection of the boundaries of strictly convex bodies of ${\mathbb{R}}^d$). Associated with the set of lengths of such orthogeodesics, we define a geometric Epstein function and prove its meromorphic continuation. We compute its residues in terms of intrinsic volumes of the convex sets. We also prove Poisson-type summation formulae relating the set of lengths of orthogeodesics and the spectrum of magnetic Laplacians.