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Weyl Subconvexity for $\mathrm{GL}_2$ with Simple Supercuspidal Ramification

Number Theory 2026-08-05 v1

Abstract

We establish Weyl-type subconvexity bounds in the level aspect for cuspidal automorphic representations of GL2/F\mathrm{GL}_2/F with simple supercuspidal ramification at a prime ideal q\mathfrak{q}. More precisely, for the family Ftζ(q3;ω)\mathcal{F}_t^\zeta(\mathfrak{q}^3;\omega) consisting of representations of conductor q3\mathfrak{q}^3, central character ω\omega, and prescribed simple supercuspidal local component, we prove the fourth moment estimate \begin{align*} \sum_{\substack{\pi \in \mathcal{F}_{t}^{\zeta}(\mathfrak{q}^3;\omega) \\ C_v(\pi) \leq \mathbf{C}_v,\ v \mid \infty}} |L(1/2,\pi)|^4 \ll_{F,\varepsilon} \mathbf C_\infty^{1+\varepsilon} N_F(\mathfrak{q})^{2+\varepsilon}. \end{align*} As a consequence, we deduce the Weyl-type bound \begin{align*} L(1/2,\pi) \ll_{F,\varepsilon} C_{\infty}(\pi)^{1/4+\varepsilon} C_{\mathrm{fin}}(\pi)^{1/6+\varepsilon}. \end{align*} In particular, this bound applies to a genuinely non-self-dual family of odd conductor exponent, beyond the reach of the cubic moment method.

Cite

@article{arxiv.2608.04982,
  title  = {Weyl Subconvexity for $\mathrm{GL}_2$ with Simple Supercuspidal Ramification},
  author = {Liyang Yang},
  journal= {arXiv preprint arXiv:2608.04982},
  year   = {2026}
}

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54 pages