Viscosity in a Lepton-Photon Universe

Abstract

We look at viscosity production in a universe consisting purely of leptons and photons. This is quite close to what the Universe actually look like when the temperature was between $10^{10}$ K and $10^{12}$ K ($1$ -- $100$ MeV). By taking the strong force and the hadronic particles out of the equation, we can examine how the viscous forces behave with all the 12 leptons present. By this we study how shear- and (more interestingly) bulk viscosity is affected during periods with particle annihilation. We use the theory given by Hoogeveen et. al. from 1986, replicate their 9-particle results and expanded it to include the muon and tau particles as well. This will impact the bulk viscosity immensely for high temperatures. We will show that during the beginning of the lepton era, when the temperature is around 100 MeV, the bulk viscosity will be roughly 100 million times larger with muons included in the model compared to a model without.

14 pages, 10 figures + 2 tables in pdf format (= 12 figures)

References in corpus (2)

• Dark Energy and Viscous Cosmology
• Brane Viscous Cosmology in the Plasma Era

Cited by in corpus (7)

• Viscous Cosmology for Early- and Late-Time Universe
• On Effective Degrees of Freedom in the Early Universe
• Remarks on cosmological bulk viscosity in different epochs
• Gravitational Waves in the Presence of Viscosity
• Viscous attenuation of gravitational waves propagating through an inhomogeneous background
• Entropy Production in a Lepton-Photon Universe
• Diffusion coefficients and constraints on hadronic inhomogeneities in the early universe