On second eigenvalues of closed hyperbolic surfaces for large genus

In this article, we study the second eigenvalues of closed hyperbolic surfaces for large genus. We show that for every closed hyperbolic surface $X_g$ of genus $g$ $(g\ge 3)$, up to uniform positive constants multiplications, the second eigenvalue ${\lambda }_2(X_g)$ of $X_g$ is greater than $\frac{{\mathcal{L}}_2(X_g)}{g^2}$ and less than ${\mathcal{L}}_2(X_g)$; moreover these two bounds are optimal as $g\to \mathrm{\infty }$. Here ${\mathcal{L}}_2(X_g)$ is the shortest length of simple closed multi-geodesics separating $X_g$ into three components. Furthermore, we also investigate the quantity $\frac{{\lambda }_2(X_g)}{{\mathcal{L}}_2(X_g)}$ for random hyperbolic surfaces of large genus. We show that as $g\to \mathrm{\infty }$, a generic hyperbolic surface $X_g$ has $\frac{{\lambda }_2(X_g)}{{\mathcal{L}}_2(X_g)}$ uniformly comparable to $\frac{1}{\ln (g)}$.