Potentials and Chern forms for Weil-Petersson and Takhtajan-Zograf metrics on moduli spaces (1508.02102v2)

Abstract: For the TZ metric on the moduli space $\mathscr{M}{0,n}$ of $n$-pointed rational curves, we construct a K\"ahler potential in terms of the Fourier coefficients of the Klein's Hauptmodul. We define the space $\mathfrak{S}{g,n}$ as holomorphic fibration $\mathfrak{S}{g,n}\rightarrow\mathfrak{S}{g}$ over the Schottky space $\mathfrak{S}{g}$ of compact Riemann surfaces of genus $g$, where the fibers are configuration spaces of $n$ points. For the tautological line bundles $\mathscr{L}{i}$ over $\mathfrak{S}{g,n}$ we define Hermitian metrics $h{i}$ in terms of Fourier coefficients of a covering map $J$ of the Schottky domain. We define the regularized classical Liouville action $S$ and show that $\exp{S/\pi}$ is a Hermitian metric in the line bundle $\mathscr{L}=\otimes_{i=1}^{n}\mathscr{L}_{i}$ over $\mathfrak{S}{g,n}$. We explicitly compute the Chern forms of these Hermitian line bundles $$c{1}(\mathscr{L}{i},h{i})=\frac{4}{3}\omega_{\mathrm{TZ},i},\quad c_{1}(\mathscr{L},\exp{S/\pi})=\frac{1}{\pi^{2}}\omega_{\mathrm{WP}}.$$ We prove that a smooth real-valued function $-\mathscr{S}=-S+\pi\sum_{i=1}^{n}\log h_{i}$ on $\mathfrak{S}_{g,n}$, a potential for this special difference of WP and TZ metrics, coincides with the renormalized hyperbolic volume of a corresponding Schottky $3$-manifold. We extend these results to the quasi-Fuchsian groups of type $(g,n)$.