Zeros of Rankin-Selberg $L$-functions in families
Peter Humphries, Jesse Thorner
Abstract
Let $\mathfrak{F}_n$ be the set of all cuspidal automorphic representations $π$ of $\mathrm{GL}_n$ with unitary central character over a number field $F$. We prove the first unconditional zero density estimate for the set $\mathcal{S}=\{L(s,π\timesπ')\colonπ\in\mathfrak{F}_n\}$ of Rankin-Selberg $L$-functions, where $π'\in\mathfrak{F}_{n'}$ is fixed. We use this density estimate to establish (i) a hybrid-aspect subconvexity bound at $s=\frac{1}{2}$ for almost all $L(s,π\timesπ')\in \mathcal{S}$, (ii) a strong on-average form of effective multiplicity one for almost all $π\in\mathfrak{F}_n$, and (iii) a positive level of distribution for $L(s,π\times\tildeπ)$, in the sense of Bombieri-Vinogradov, for each $π\in\mathfrak{F}_n$.
