Stieltjes–Bethe equations in higher genus and branched coverings with even ramifications

Abstract

We describe projective structures on a Riemann surface corresponding to monodromy groups which have trivial SL(2) monodromies around singularities and trivial PSL(2) monodromies along homologically non-trivial loops on a Riemann surface. We propose a natural higher genus analog of Stieltjes–Bethe equations. Links with branched projective structures and with Hurwitz spaces with ramifications of even order are established. We find a higher genus analog of the genus zero Yang–Yang function (the function generating accessory parameters) and describe its similarity and difference with Bergman tau-function on the Hurwitz spaces.