"Before inflation, before the Big Bang ... you get into branes and the cyclic universe", Sean M. Carroll interviewed by Edge magazine.
"Inflation does not provide a natural explanation for why the early universe looks like it does unless you can give me an answer for why inflation ever started in the first place. That is not a question we know the answer to right now. That is why we need to go back before inflation into before the Big Bang, into a different part of the universe to understand why inflation happened versus something else. There you get into branes and the cyclic universe. ... I really don't like any of the models that are on the market right now. We really need to think harder about what the universe should look like."
Sean M. Carroll is a theoretical physicist, is a senior research associate at Caltech. Cofounder and contributor to the Cosmic Variance blog, his research interests include theoretical aspects of cosmology, field theory, and gravitation. He is the author of a Spacetime and Geometry: An Introduction to General Relativity; and From Eternity to Here: The Quest for the Ultimate Theory of Time. He is a frequent commentator on theoretical physics within the media.