Effective log-free zero density estimates for automorphic $L$-functions and the Sato-Tate conjecture

Abstract

Let $K/\mathbb{Q}$ be a number field. Let $\pi$ and $\pi^\prime$ be cuspidal automorphic representations of $\mathrm{GL}_d(\mathbb{A}_K)$ and $\mathrm{GL}_{d^\prime}(\mathbb{A}_K)$, and suppose that either both $d$ and $d'$ are at most 2 or at least one of $\pi$ and $\pi^\prime$ is self-dual. When $d=d^\prime=2$, we prove an unconditional and effective log-free zero density estimate for the Rankin-Selberg $L$-function $L(s,\pi\otimes\pi^\prime,K)$. For other choices of $d$ and $d^\prime$, we obtain similar results assuming that either $\pi$ or $\pi^\prime$ satisfies the generalized Ramanujan conjecture. With these density estimates, we make effective the Hoheisel phenomenon of Moreno regarding primes in short intervals and extend it to the context of the Sato-Tate conjecture; additionally, we bound the least prime in the Sato-Tate conjecture in analogy with Linnik's theorem on the least prime in an arithmetic progression. When $K=\mathbb{Q}$, we also prove an effective log-free density estimate for $L(s,\pi\otimes\pi^\prime,\mathbb{Q})$ averaged over twists by Dirichlet characters. With this second density estimate, we prove an averaged form of the prime number theorem in short intervals for $L(s,\pi\otimes\tilde{\pi},\mathbb{Q})$ when $\pi$ is a cuspidal automorphic representation of $\mathrm{GL}_2(\mathbb{A}_{\mathbb{Q}})$.