The (2,5) minimal model on genus two surfaces
Abstract
In the (2,5) minimal model, the partition function for genus g=2 Riemann surfaces is given by a 5-tuple of functions with appropriate transformation under the mapping class group. These functions generalise the two Rogers-Ramanujan functions for the torus. Their expansions around a locus of surfaces with conical singularities in the interior of the g=2 Siegel upper half plane are obtained in terms of standard modular forms. The dependence on the metric is controlled by a canonical choice of flat surface metrics. In the alternative case where a handle of the g=2 surface is pinched, our method requires knowledge of the two-point function of the fundamental lowest-weight vector in the non-vacuum representation of the Virasoro algebra, for which we derive a 3rd order ODE. In order to make the paper more accessible to mathematicians, the exposition includes a short introduction to conformal field theory on Riemann surfaces, which may be of independent interest.