Gauge-invariant gravitational wave modes in pre-big bang cosmology
Physics Department, Bishop’s University, 2600 College Street, Sherbrooke, Québec, J1M 1Z7, Canada
Revised: 22 August 2010
Published online: 25 September 2010
The t<0 branch of pre-big bang cosmological scenarios is subject to a gravitational wave instability. The unstable behaviour of tensor perturbations is derived in a very simple way in Hwang’s covariant and gauge-invariant formalism developed for extended theories of gravity. A simple interpretation of this instability as the effect of an “antifriction” is given, and it is argued that a universe must eventually enter the expanding phase.
© Springer-Verlag / Società Italiana di Fisica, 2010