Speaker
Frank Koennig
(Institut fuer Theoretische Physik -Uni Heidelberg, Germany)
Description
Bimetric theory describes gravitational interactions in the presence of an extra
spin-2 field. It allows for many different types of cosmological
solutions but not all of them are theoretically allowed, most of them are
generically plagued by instabilities. We discuss the
conditions of the absence of these ghost- and gradient instabilities and present
a ghost-free model in which the gradient instabilities can be pushed back to
unobservably early times. In this limit, the theory approaches general
relativity with a technically-natural effective cosmological constant which is, remarkably,
determined by the spin-2 interaction scale.
