### Speaker

### Description

"After reviewing some key hints and puzzles from the early

universe, I will introduce recent joint work with Neil Turok

suggesting a rigid and predictive new approach to addressing them.

Our universe seems to be dominated by radiation at early times, and positive vacuum energy at late times. Taking the symmetry and analyticity properties of such a spacetime seriously leads to a new formula for the gravitational entropy of our universe, and a picture in which the Big Bang may be regarded as a kind of mirror.

I will explain how this line of thought suggests new explanations for a number of observed properties of the universe, including: its homogeneity, isotropy and flatness; the arrow of time (i.e. the fact that entropy increases *away* from the bang); several properties of the primordial perturbations; the nature of dark matter (which, in this picture, is a right-handed neutrino, radiated from the early universe like Hawking radiation from a black hole); the origin of the

primordial perturbations; and even the existence of three generations of standard model fermions. I will discuss some observational predictions that will be tested in the coming decade, and some key open questions."

### External references

- 23050112
- 5e214144-e4db-45d1-9738-9a0d5f5d008b
- 90798393-67b4-4c19-95b7-f7bdd6520f0f