The origin of the graviton from string theory is well understood: it corresponds to a massless state in closed spectra, whose low-energy effective action, as extracted scattering amplitudes, that Einstein-Hilbert. In this work, we explore possibility such string-theoretic emergence ghost-free bimetric theory, recently proposed involves two dynamical metrics, around particular backgrounds propag...

We derive how to incorporate topological features of Riemann surfaces in string amplitudes by insertions bi-local operators called handle operators. The resulting formalism is exact and globally well-defined moduli space. After a detailed pedagogical discussion surfaces, complex structure deformations, global vs local aspects, boundary terms, an explicit choice gluing-compatible (modulo U(1)) c...