English

Beyond endoscopy for $\mathsf{GL}_2$ over $\mathbb{Q}$ with ramification 4: contribution of non-elliptic parts

Number Theory 2026-05-21 v1 Representation Theory

Abstract

We continue our work on GL2\mathsf{GL}_2 over Q\mathbb{Q} in the ramified setting for \emph{Beyond Endoscopy}. We establish asymptotic formulas for each term of the trace formula when summing over n<Xn<X, using arbitrary smooth test functions at the places in S={,q1,,qr}S=\{\infty,q_1,\dots, q_r\} where 2S2\in S, for the standard representation, up to an error of o(X)o(X). This yields an identity depending on a parameter XX, leading to certain identities that can be regarded as a limit form of the trace formula for GL2\mathsf{GL}_2 over Q\mathbb{Q}. On the spectral side, we employ the contour shift method and the Riemann-Lebesgue lemma. On the geometric side, both the identity part and the unipotent part contribute o(X)o(X). The elliptic part was reduced to the hyperbolic part in a previous paper. Finally, using hyperbolic Poisson summation, we relate the hyperbolic part back to the spectral side and determine its contribution.

Keywords

Cite

@article{arxiv.2605.20719,
  title  = {Beyond endoscopy for $\mathsf{GL}_2$ over $\mathbb{Q}$ with ramification 4: contribution of non-elliptic parts},
  author = {Yuhao Cheng},
  journal= {arXiv preprint arXiv:2605.20719},
  year   = {2026}
}