Based on concepts drawn from the ekpyrotic scenario and M-theory, we elaborate our recent proposal of a cyclic model of the Universe. In this model, the Universe undergoes an endless sequence of cosmic epochs which begin with the Universe expanding from a ‘big bang’ and end with the Universe contracting to a ‘big crunch.’ Matching from ‘big crunch’ to ‘big bang’ is performed according to the pr...

Inflationary theory was proposed 20 years ago. In the beginning it looked like an interesting piece of science fiction. During the last 20 years it changed quite a lot and became a broadly accepted cosmological paradigm. New versions of this theory do not require any assumptions about initial thermal equilibrium in the early universe. Inflation is no longer based on the mechanism of supercoolin...

We show why the universe started in an unstable de Sitter state. The quantum origin of our universe implies one must take a 'top down' approach to the problem of initial conditions in cosmology, in which the histories that contribute to the path integral, depend on the observable being measured. Using the no boundary proposal to specify the class of histories, we study the quantum cosmological ...