Anisotropic Gravitational Wave Background from Preheating

Series: 
The London Relativity and Cosmology Seminar
Speaker: 
Laura Bethke (Imperial)
Date: 
October 23rd, 2013 at 16:30
Room: 
Maths 103
Abstract: 

Gravitational Waves (GWs) should be produced in many different astrophysical and cosmological settings, and measuring the primordial GW background could provide us with new insights into the physics of the early Universe.

One example of GW production in the early Universe is preheating; a violent, non-equilibrium process after inflation. It is characterised by an efficient transfer of energy from the decaying inflaton to other particles, often by parametric resonance. This sources the fast growth of fluctuations in the fields, leading to large inhomogeneities and hence copious production of GWs.

I will describe how for the specific model of massless preheating the generated background of GWs should be anisotropic on large scales today, with relative fluctuations of the order of 1%. We believe that this anisotropy is a general feature of models in which a light scalar field is present, as long as certain conditions for the preheating mechanism are met. Studying GWs from preheating might therefore eventually enable us to distinguish between different models of inflation.