High Energy Theory Seminar

We study the quantum cosmology of a universe with conformal matter. For homogeneous, isotropic metrics and matter, the quantum gravitational path integral may be performed exactly. The result is a "perfect bounce," in which the universe passes smoothly across the big bang singularity. We extend this treatment to include anisotropies and generic inhomogeneous perturbations, treated at both linear and nonlinear order, providing evidence for a consistent semi-classical description in which all fields pass "around" the cosmological singularity along complex classical paths. We show that the non-linearities lead to a breakdown in perturbation theory at large times, signalling the formation of shocks in the very early universe, a classical phenomenon of interest in its own right.