Linear programming bounds for hyperbolic surfaces
Maxime Fortier Bourque, Bram Petri
TL;DR
This work extends linear programming bounds, originally developed for sphere packings, to closed hyperbolic surfaces by leveraging the Selberg trace formula and carefully constructed test functions. The authors derive rigorous upper bounds for five geometric/spectral invariants—sys, kiss, $\lambda_1$, $m_1$, and $N_{\mathrm{small}}$—valid across genus, with strong performance in low genus and robust asymptotics as genus grows; they also obtain lower bounds on systole that yield spectral gaps $>1/4$ in several genera. The approach unifies the bounds via a common LP framework, combining algebraic (polynomial) and Bessel-function-based test functions, interval arithmetic, and ancillary computational proofs to certify results. The results advance the understanding of optimal geometric and spectral configurations on hyperbolic surfaces and provide near-term pathways toward global bounds and Ramanujan-like phenomena across genera. Practical impact includes sharper universal inequalities and a framework for certifiable numerical proofs in spectral geometry.
Abstract
We adapt linear programming methods from sphere packings to closed hyperbolic surfaces and obtain new upper bounds on their systole, their kissing number, the first positive eigenvalue of their Laplacian, the multiplicity of their first eigenvalue, and their number of small eigenvalues. Apart from a few exceptions, the resulting bounds are the current best known both in low genus and as the genus tends to infinity. Our methods also provide lower bounds on the systole (achieved in genus $2$ to $7$, $14$, and $17$) that are sufficient for surfaces to have a spectral gap larger than $1/4$.
