Pre-inflation: origin of the Universe from a topological phase   transition
  I study a model which describes the birth of the universe using a global topological phase transition with a complex manifold where the time, $\tau$, is considered as a complex variable. Before the big bang $\tau$ is a purely imaginary variable so that the space can be considered as Euclidean. The phase transition from a pre-inflation to inflation is examined by studying the dynamical rotation of the time on the complex plane. Back-reaction effects are exactly calculated using Relativistic Quantum Geometry. 
Mauricio Bellini (IFIMAR - CONICET and UNMdP)
gr-qc hep-th