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arXiv · 2410.23233

$\mathrm{SL}_2$-character varieties of $2$-generated groups and failure of weak integrality

Benjamin Church·Francisco García-Cortés
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Abstract

Let $\ell$ be a prime number, $k$ a positive integer and consider the group $\Gamma_{\ell^k} :=\langle a,b\ \vert\ a^{\ell^k(\ell^k-1)}ba^{-\ell^k}b^{-2}\rangle$. We prove that $\Gamma_{\ell^k}$ is not $\mathrm{SL}_2$-weakly integral with obstruction at exactly the prime $\ell$. We also give a general description of the character varieties of $2$-generated groups with a relation of the form $a^{n_1} b^{m_1} a^{n_2} b^{m_2} = 1$.

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Benjamin Church, Francisco García-Cortés. 2024-10-30. $\mathrm{SL}_2$-character varieties of $2$-generated groups and failure of weak integrality. https://arxiv.org/abs/2410.23233

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