Speaker
Dr
Norihiro TANAHASHI
(DAMTP, University of Cambridge)
Description
We study cosmological perturbations in bimetric theory
focusing on the
effect of coupling of matter fields to metrics. Firstly we
review the
results for the case that a matter field couples to the physical
metric and the other one couples to the second metric, in
which a
stable cosmology can be realized once physically sensible
conditions
are satisfied. Next we study the case that a matter field
couples to a
composite metric made out of the two metrics, in which a matter
couples to the two metrics simultaneously without
introducing the
Boulware-Deser ghost. We find that some cosmological
solutions which
is stable in the former case is destabilized in the latter
case, while
there is a class of solutions which is unstable in the
former case but
could be made viable in the latter case. We argue possible
usages of
this new class of stable solutions.
