Laplacians in spinor bundles over translation surfaces: self-adjoint extentions and regularized determinants

We study the regularized determinants \({\rm det}\, \Delta\) of various self-adjoint extensions of symmetric Laplacians acting in spinor bundles over compact Riemann surfaces with flat singular metrics \(|\omega|^2\), where \(\omega\) is a holomorphic one form on the Riemann surface. We find an explicit expression for \({\rm det}\, \Delta\) for the so-called self-adjoint Szeg\"o extension through the Bergman tau-function on the moduli space of Abelian differentials and the theta-constants (corresponding to the spinor bundle). This expression can be considered as a version of the well-known spin-\(1/2\) bosonization formula of Bost-Nelson for the case of flat conformal metrics with conical singularities and a higher genus generalization of the Ray-Singer formula for flat elliptic curves. We establish comparison formulas for the determinants of two different extensions (e. g., the Szeg\"o extension and the Friedrichs one). The paper answers a question raised by D'Hoker and Phong \cite{DH-P} more than thirty years ago. We also reconsider the results from \cite{DH-P} on the regularization of diverging determinant ratio for Mandelstam metrics (for any spin) proposing (and computing) a new regularization of this ratio.