In 2011, F. Hassan and R. Rosen achieved the construction of the first gosth-free theory of two interacting spin-2 fields. But despite its great elegance and interesting phenomenological implications, this theory of "bigravity" suffers from a gradient-type instability. Moreover, it postulates the existence of vectorial and scalar gravitational modes, the latter being severely constrained by observations of binary pulsars. This stimulated us to construct a "minimal" theory of bigravity, ie. a theory of two interacting spin-2 fields that propagates only four tensorial degrees of freedom. This talk will first introduce the motivations that led to this "minimal" theory of bigravity, and review its construction by a Hamiltonian procedure. I will then present its cosmological phenomenology, and show that it provides a stable nonlinear completion of the cosmology of the Hassan-Rosen bigravity. We will end by discussing interesting phenomenological features and possible ways to test the theory.
Event organized by CEICO, Central European Institute for Cosmology and Fundamental Physics.
Please contact Roberto Oliveri or Gizem Sengor for further info.