Relic abundance

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.

Uses

Relic abundance is modelled for WIMPs (weakly interacting massive particles) in the study of dark matter.¹

Calculation

Assuming that an elementary particle was formerly in thermal equilibrium, its relic abundance may be calculated using a Boltzmann equation.²

The temperature scaled abundance of a particle is defined³ by

Y\equiv {\frac {n}{T^{3}}}

where $n$ is the number density:

n\equiv {\frac {N}{V}}

that is, number of particles per physical volume (not the comoving volume).

The relic abundance of a particle is shown by $Y_{\infty }$ indicates the asymptotic value of abundance of a species of a particle which it will reach after its "freeze-out".⁴

References

Kim Griest, "Relic Abundance in More Detail" Archived 2017-01-27 at the Wayback Machine, The Net Advance of Physics: The Nature of Dark Matter, Section 6C, MIT
J. Thanh Van Tran (1 January 1990). Z0 Physics: Proceedings of the XXVth Rencontre de Moriond, Les Arcs, Savoie, France, March 4-11, 1990. Atlantica Séguier Frontières. p. 306. ISBN 978-2-86332-081-5.
Scott Dodelson (2003). Modern Cosmology. Academic Press. pp. 74–76. ISBN 978-0-12-219141-1.
Patrick Petter (28 October 2013). Basic Knowledge of Astrophysic: A New Way. epubli. p. 91. ISBN 978-3-8442-7203-1.

[1] Kim Griest, "Relic Abundance in More Detail" Archived 2017-01-27 at the Wayback Machine, The Net Advance of Physics: The Nature of Dark Matter, Section 6C, MIT

[Tran1990-2] J. Thanh Van Tran (1 January 1990). Z0 Physics: Proceedings of the XXVth Rencontre de Moriond, Les Arcs, Savoie, France, March 4-11, 1990. Atlantica Séguier Frontières. p. 306. ISBN 978-2-86332-081-5.

[Dodelson2003-3] Scott Dodelson (2003). Modern Cosmology. Academic Press. pp. 74–76. ISBN 978-0-12-219141-1.

[Petter2013-4] Patrick Petter (28 October 2013). Basic Knowledge of Astrophysic: A New Way. epubli. p. 91. ISBN 978-3-8442-7203-1.

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