In this video I go through the different theories which physicists have for how the universe began. To learn more about inflation and the inflaton field, this is an excellent starting point: https://arxiv.org/abs/0907.5424 Here is more about the Ekpyrotic Universe: https://arxiv.org/abs/hep-th/0103239 I wrote about Penrose's Cyclic Cosmology here: http://backreaction.blogspot.com/2018/08/roger-penrose-still-looks-for-evidence.html You find more about the idea that universes are born inside black holes in Zeeya Merali's book: https://www.amazon.com/Big-Bang-Little-Room-Universes/dp/0465065910 The idea that the universe started from a 4+1 dimensional black hole is explained here: https://www.nature.com/news/did-a-hyper-black-hole-spawn-the-universe-1.13743 I have explained the idea of "Asymptotic Silence" here http://backreaction.blogspot.com/2014/01/a-moment-of-silence-replaces-big-bang.html Finally, the theory of String Gas Cosmology is from Robert Brandenberger: https://arxiv.org/abs/0808.0746