On Effective Degrees of Freedom in the Early Universe

2016/09/16 by Lars Husdal · 1 voice · 19 citations
Earth and Planetary Sciences · Physics and Astronomy · #Advanced Mathematical Theories and Applications #Earth Systems and Cosmic Evolution #High-Energy Particle Collisions Research #astro-ph.CO #hep-ph

paper · pdf · doi:10.3390/galaxies4040078

openalex created_date 2016/09/30 · openalex publication_date 2016/12/17 · openalex updated_date 2026/07/29

Abstract

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.

Citations

• Observation of a new particle in the search for the Standard Model Higgs boson with the ATLAS detector at the LHC
• NINE-YEAR <i>WILKINSON MICROWAVE ANISOTROPY PROBE</i> ( <i>WMAP</i> ) OBSERVATIONS: FINAL MAPS AND RESULTS

Cited by

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• Beyond Standard Model equation of state and primordial black holes
• Dynamically generated tilt of isocurvature fluctuations
• Big Bang Nucleosynthesis constraints on space-time noncommutativity
• Gravitational capture of magnetic monopoles by primordial black holes in the early universe
• Revisiting axion dark matter with nonlinear transitions
• NLO observables for QCD-like theories and application to pion dark matter
• Big Bang Nucleosynthesis constraints on the cosmological evolution in a Universe with a Weylian Boundary
• Z₄ scotogenic model with a Higgs portal
• Cosmic string gravitational wave backgrounds at LISA: I. Signal survey, template reconstruction, and model comparison
• A New Source of Phase Transition Gravitational Waves: Heavy Particle Braking Across Bubble Walls
• νp-process in Core-Collapse Supernovae: Imprints of General Relativistic Effects

Discussions

• The universe cools ( adiabatically ) as it expands. The heat added by matter-antimatter annihilation delays that cooling. Think of annihilation as a phase transition. For temperatures $T$ higher than [stackexchange, 21 points]

Related

• Thermodynamic and cosmological parameters of early stages of the Universe
• Particle properties in the early universe from the contraction of the SM gauge group
• Reliable Equations of State of Viscous Strong and Electroweak Matter
• Quarks to Cosmos: Particles and Plasma in Cosmological evolution
• Theory of the Quark-Gluon Plasma