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LOCAL AVERAGE OF THE HYPERBOLIC CIRCLE PROBLEM FOR FUCHSIAN GROUPS
Published online by Cambridge University Press: 06 February 2018
Abstract
Let $\unicode[STIX]{x1D6E4}\subseteq \operatorname{PSL}(2,\mathbf{R})$ be a finite-volume Fuchsian group. The hyperbolic circle problem is the estimation of the number of elements of the
$\unicode[STIX]{x1D6E4}$-orbit of
$z$ in a hyperbolic circle around
$w$ of radius
$R$, where
$z$ and
$w$ are given points of the upper half plane and
$R$ is a large number. An estimate with error term
$\text{e}^{(2/3)R}$ is known, and this has not been improved for any group. Recently, Risager and Petridis proved that in the special case
$\unicode[STIX]{x1D6E4}=\operatorname{PSL}(2,\mathbf{Z})$ taking
$z=w$ and averaging over
$z$ in a certain way the error term can be improved to
$\text{e}^{(7/12+\unicode[STIX]{x1D716})R}$. Here we show such an improvement for a general
$\unicode[STIX]{x1D6E4}$; our error term is
$\text{e}^{(5/8+\unicode[STIX]{x1D716})R}$ (which is better than
$\text{e}^{(2/3)R}$ but weaker than the estimate of Risager and Petridis in the case
$\unicode[STIX]{x1D6E4}=\operatorname{PSL}(2,\mathbf{Z})$). Our main tool is our generalization of the Selberg trace formula proved earlier.
MSC classification
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- Research Article
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- Copyright
- Copyright © University College London 2018
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