Next Article in Journal
Conical Stream of the Two-Sided Jets in NGC 4261 over the Range of 103–109 Schwarzschild Radii
Previous Article in Journal
Asymmetric Star Formation Efficiency Due to Ram Pressure Stripping
Open AccessArticle

On Effective Degrees of Freedom in the Early Universe

Department of Physics, Norwegian University of Science and Technology, N-7491 Trondheim, Norway
Academic Editor: Emilio Elizalde
Galaxies 2016, 4(4), 78; https://doi.org/10.3390/galaxies4040078
Received: 20 October 2016 / Revised: 8 December 2016 / Accepted: 8 December 2016 / Published: 17 December 2016
We explore the effective degrees of freedom in the early Universe, from before the electroweak scale at a few femtoseconds after the Big Bang until the last positrons disappeared a few minutes later. We look at the established concepts of effective degrees of freedom for energy density, pressure, and entropy density, and introduce effective degrees of freedom for number density as well. We discuss what happens with particle species as their temperature cools down from relativistic to semi- and non-relativistic temperatures, and then annihilates completely. This will affect the pressure and the entropy per particle. We also look at the transition from a quark-gluon plasma to a hadron gas. Using a list a known hadrons, we use a “cross-over” temperature of 214 MeV, where the effective degrees of freedom for a quark-gluon plasma equals that of a hadron gas. View Full-Text
Keywords: viscous cosmology; shear viscosity; bulk viscosity; lepton era; relativistic kinetic theory viscous cosmology; shear viscosity; bulk viscosity; lepton era; relativistic kinetic theory
Show Figures

Figure 1

MDPI and ACS Style

Husdal, L. On Effective Degrees of Freedom in the Early Universe. Galaxies 2016, 4, 78. https://doi.org/10.3390/galaxies4040078

AMA Style

Husdal L. On Effective Degrees of Freedom in the Early Universe. Galaxies. 2016; 4(4):78. https://doi.org/10.3390/galaxies4040078

Chicago/Turabian Style

Husdal, Lars. 2016. "On Effective Degrees of Freedom in the Early Universe" Galaxies 4, no. 4: 78. https://doi.org/10.3390/galaxies4040078

Find Other Styles
Note that from the first issue of 2016, MDPI journals use article numbers instead of page numbers. See further details here.

Article Access Map by Country/Region

1
Search more from Scilit
 
Search
Back to TopTop