http://arxiv.org/abs/2001.03633
Heavy-ion colliders have revealed the process of “fast thermalization”. This experimental break-through has led to new theoretical tools to study the thermalization process at both weak and strong coupling. We apply this to the reheating epoch of inflationary cosmology, and the formation of a cosmological quark gluon plasma (QGP). We compute the thermalization time of the QGP at reheating, and find it is determined by the energy scale of inflation and the shear viscosity to entropy ratio $\eta/s$; or equivalently, the tensor-to-scalar ratio and the strong coupling constant at the epoch of thermalization. Thermalization is achieved near-instantaneously in low-scale inflation and in strongly coupled systems, and takes less than an e-fold of expansion for weakly-coupled systems or after high-scale inflation. We then consider the potential for observing this process: we demonstrate that the cosmic microwave background is largely insensitive, and the shift in $n_s$ and $r$ is well below the sensitivity of CMB S4 and Simons Observatory. We also find a stochastic background of gravitational waves at frequencies accessible by interferometers, albeit at a level unobservable by even next generation experiments.
E. McDonough
Tue, 14 Jan 20
63/72
Comments: 7 pages