Big Bang as a critical point
  This essay addresses the issue of gravitational phase transitions in the
early universe. We suggest that a second order phase transition observed in the
Causal Dynamical Triangulations approach to quantum gravity may have a
cosmological relevance. The phase transition interpolates between a
non-geometric crumpled phase of gravity, and an extended phase with classical
properties. Transitions of this kind have been postulated earlier in the
context of geometrogenesis in Quantum Graphity. We show that critical behavior
may also be associated with a signature change event in Loop Quantum Cosmology.
In both cases, classical spacetime originates at the critical point associated
with a second order phase transition.
