Canonical Exorcism for Cosmological Ghosts

Synopsis

We discuss time-dependent classical and quantum canonical transformation. In particular, we demonstrated that for the quantum canonical transformations the Hamiltonian is transformed as a connection in non-abelian gauge theories. We explicitly construct such quantum and classical transformations which change the sign the Hamiltonian. Hence one can canonically transform a ghost into a field with the correct standard sign in front of the quadratic action. Therefore the usual naive criteria for the presence or absence of ghost-like vacuum instabilities on time-dependent backgrounds are not well physically motivated and the actual information about instabilities is hidden in the interactions.

http://www.sfu.ca/physics-archive/cosmology/seminars/2016-08-04.html