Extracting Bigravity from string amplitudes

The origin of the graviton from string theory is well understood: it corresponds to a massless state in closed string spectra, whose low-energy effective action, as extracted from string scattering amplitudes, is that of Einstein-Hilbert.In this talk, we will discuss our recent published work on the possibility of such a string-theoretic emergence of ghost-free bimetric theory, a recently proposed extension of general relativity that involves two dynamical metrics and which around particular backgrounds propagates the graviton and a massive spin-2 field, with the latter having been put forward as a viable dark matter candidate.