The goal of this talk is to discuss the variance of sums of the divisor function leading to certain random matrix distributions. While the knowledge of these problems is quite limited over the natural numbers, much more is known over function fields. We will start by introducing the basics of zeta functions and $L$-functions over function fields. We will then discuss the work of Keating, Rodgers, Roditty-Gershon, and Rudnick on the sums over arithmetic progressions, leading to distributions over unitary matrices by the Katz and Sarnak philosophy and a general conjecture over the natural numbers. Finally, we will present some recent work (in collaboration with Kuperberg) on sums over squares modulo a prime leading to symplectic distributions.
In this talk, we will discuss the logarithm of the central value $L\left(\frac{1}{2}, \chi_D\right)$ in the symplectic family of Dirichlet $L$-functions associated with the hyperelliptic curve of genus $g$ over a fixed finite field $\mathbb{F}_q$ in the limit as $g\to \infty$. Unconditionally, we show that the distribution of $\log \big|L\left(\frac{1}{2}, \chi_D\right)\big|$ is asymptotically bounded above by the full Gaussian distribution of mean $\frac{1}{2}\log \deg(D)$ and variance $\log \deg(D)$, and also $\log \big|L\left(\frac{1}{2}, \chi_D\right)\big|$ is at least $94.27 \%$ Gaussian distributed. Assuming a mild condition on the distribution of the low-lying zeros in this family, we obtain the full Gaussian distribution.