Dimitrios Lekkas | Searcharxiv

arXiv2025

A relative trace formula and counting geodesic arcs in the hyperbolic plane

We study a modification of the hyperbolic circle problem: instead of all elements of a Fuchsian group $\Gamma$, we consider the double cosets by two hyperbolic subgroups. This has a geometric interpretation in terms of the number of common perpendiculars between two closed geodesics for $\Gamma \backslash\mathbb{H}$. We prove an explicit relative trace formula, which is flexible for the counting problem. Using a large sieve inequality developed by the first author and Voskou, we prove a new bound in mean square for the error term of order $O(X^{1/2}\log X)$. We conjecture that this is the correct order of growth. Along the way we provide a new proof of the pointwise error bound $O(X^{2/3})$, originally proved by Good.

math.NT↗

arXiv2024

Large Sieve Inequalities for periods of Maass forms

For $\Gamma$ a Fuchsian Group of the first kind, we obtain large sieve inequalities with weights the hyperbolic periods of Maass forms of even weight. This is inspired by work of Chamizo, who proved a large sieve inequality with weights values of Maass forms of weight $0$. The motivation is applications in counting problems in $\Gamma_1 \backslash \Gamma / \Gamma_2$, where $\Gamma_1$, $\Gamma_2$ are hyperbolic subgroups of $\Gamma$.

math.NT↗