Physics (Internal)

Effective Approaches in Cosmology: Large Scale Structure, Baryon Asymmetry, and the Dark Sector

This event is part of the HET Seminar Series.

Abstract: A range of beautiful cosmological observations, including the CMB and large scale structure, have led to a range of deep theoretical puzzles. This includes understanding the origin and evolution of cosmological fluctuations, the origin of the baryon (or matter/anti-matter) asymmetry, and the character of the dark/vacuum sectors. In this talk I will employ the principles of effective field theory to address some aspects of these puzzles. Firstly, I will describe a systematic examination of the large scale structure in terms of an effective fluid. I will describe (i) the properties of this fluid on sub-horizon scales, (ii) its renormalization and perturbation theory, (iii) the explicit measurement of its fluid parameters, and (iv) the computation of the power spectrum. Secondly, I will describe a simple effective Lagrangian that unifies the physics of early universe inflation and the physics of the baryon asymmetry. I will describe its observational consequences, and also present the effective theory of Goldstone modes in the post-inflationary era. Thirdly, I will review the systematic use of effective field theory to unravel the weak force, the Higgs, and the stability of the vacuum. I will describe how the (in)stability of the vacuum requires new physics at high energies and how this could be related to axion dark matter.