Beyond endoscopy for $\mathsf{GL}_2$ over $\mathbb{Q}$ with ramification 3: contribution of the elliptic part

Fuente: arXiv
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Autor principal: Cheng, Yuhao
Formato: Preprint
Publicado: 2025
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author Cheng, Yuhao
author_facet Cheng, Yuhao
contents We continue to work on \emph{Beyond Endoscopy} for $\mathsf{GL}_2$ over $\mathbb{Q}$ with ramification at $S = \{\infty, q_1, \dots, q_r\}$ (where $2 \in S$), generalizing the final step of Altuğ's work in the unramified setting. We derive an explicit asymptotic formula for the elliptic part when summing over $n<X$ with arbitrary smooth test functions at places in $S$ for the standard representation. As a consequence, we obtain the desired limit for the simple trace formula which only occurs in the ramified case. Moreover, we prove an asymptotic formula for the traces of Hecke operators on cusp forms with arbitrary level and weight $>2$, directly generalizing Altuğ's final result. Our approach differs entirely from Altuğ's: We apply a second Poisson summation with respect to the determinant, obtaining a formula on the Hitchin-Steinberg base $\mathfrak{g}/\!/ \mathsf{G}$. By changing variables from $(T, N)$ to $(T, Δ)$ on $\mathfrak{g}/\!/ \mathsf{G}$, we perform analysis in the new coordinates.
format Preprint
id arxiv_https___arxiv_org_abs_2508_07167
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Beyond endoscopy for $\mathsf{GL}_2$ over $\mathbb{Q}$ with ramification 3: contribution of the elliptic part
Cheng, Yuhao
Number Theory
Representation Theory
11F72
We continue to work on \emph{Beyond Endoscopy} for $\mathsf{GL}_2$ over $\mathbb{Q}$ with ramification at $S = \{\infty, q_1, \dots, q_r\}$ (where $2 \in S$), generalizing the final step of Altuğ's work in the unramified setting. We derive an explicit asymptotic formula for the elliptic part when summing over $n<X$ with arbitrary smooth test functions at places in $S$ for the standard representation. As a consequence, we obtain the desired limit for the simple trace formula which only occurs in the ramified case. Moreover, we prove an asymptotic formula for the traces of Hecke operators on cusp forms with arbitrary level and weight $>2$, directly generalizing Altuğ's final result. Our approach differs entirely from Altuğ's: We apply a second Poisson summation with respect to the determinant, obtaining a formula on the Hitchin-Steinberg base $\mathfrak{g}/\!/ \mathsf{G}$. By changing variables from $(T, N)$ to $(T, Δ)$ on $\mathfrak{g}/\!/ \mathsf{G}$, we perform analysis in the new coordinates.
title Beyond endoscopy for $\mathsf{GL}_2$ over $\mathbb{Q}$ with ramification 3: contribution of the elliptic part
topic Number Theory
Representation Theory
11F72
url https://arxiv.org/abs/2508.07167