Weil-Petersson volumes for extended JT supergravity from ordinary differential equations

Abstract

Recent work [1] produced an efficient method for computing Weil-Petersson volumes using two ordinary differential equations (ODEs) that appear naturally in double scaled random matrix models. One is the defining string equation of the model and the other is the Gel'fand-Dikii equation satisfied by the diagonal resolvent of an auxiliary Hamiltonian used to compute correlators of macroscopic loops. In concert, when applied to Jackiw-Teitelboim gravity, the recursive expansion of these two ODEs efficiently define, order by order in genus, the Weil-Petersson volumes $V_{g,1}(b)$ for bordered hyperbolic Riemann surfaces with one geodesic boundary (length $b$) and genus $g$. The method works equally well for both ordinary and ${ N}{=}1$ supersymmetric JT gravity cases. This paper explores the method to higher genus, verifying some conjectures of ref.[1], and deriving several useful recursive formulae for general use. The method is then applied to the new examples furnished by recent matrix model definitions of JT supergravity with extended supersymmetry, and several example expressions for the volumes are derived, confirming and extending ${ N}{=}2$ examples of Turiaci and Witten, and furnishing new formulae for the cases with small and large ${ N}{=}4$ supersymmetry. The prospects for extending the ODE method to the full set of $V_{g,n}(\{ b_i\})$, ($i=1,\ldots ,n$), are discussed.