In cosmology, the relic abundance of a given elementary particle is a measure of the present quantity of that particle remaining from the Big Bang.
Contents
Uses
Relic abundance is modelled for WIMPs (weakly interacting massive particles) in the study of dark matter.
Calculation
Assuming that an elementary particle was formerly in thermal equilibrium, its relic abundance may be calculated using a Boltzmann equation.
The temperature scaled abundance of a particle is defined by
where
that is, number of particles per physical volume (not the comoving volume).
The relic abundance of a particle is shown by
Accepted abundances
The current accepted abundance values for protons, neutrons, photons, neutrinos, and WIMPs can be found in the table below: