Particle physics, which deals with the interactions
of elementary particles at high energies,
is an important component of cosmological
models of the early universe, when the universe
was dominated by radiation and its average
energy density was very high. Because of this,
pair production, scattering processes and
decay of unstable particles are important
in cosmology, and the interface between particle
physics and cosmology is sometimes referred
to as particle cosmology.
As a thumb rule, a scattering or a decay process
is cosmologically important in a certain cosmological
epoch if its relevant time scale is smaller
or even to the time scale of the universe
expansion, which is
1
H
{\displaystyle {\frac {1}{H}}}
with
H
{\displaystyle H}
being the time-dependent Hubble parameter.
This is roughly equal to the age of the universe
at that time.
For example, the pion has a lifetime of about
26 nanoseconds. This means that particle physics
processes involving pions did not take place
until roughly that much time passed since
the start of the Big Bang.
Cosmological observations of phenomena such
as the cosmic microwave background and the
cosmic abundance of elements, together with
the predictions of the Standard Model of particle
physics, place constraints on the conditions
of the early universe. The success of the
Standard Model at explaining these observations
provides a confirmation of its validity outside
of laboratory conditions. In addition, phenomena
extrapolated from cosmological observations,
such as dark matter and CP-violation, suggest
a need for physics that goes beyond the Standard
Model.
== External links ==
Center for Particle Cosmology at the University
of Pennsylvania
== Further reading ==
Allday, Jonathan (2002). Quarks, Leptons and
the Big Bang (Second ed.). ISBN 978-0-7503-0806-9.
Bergström, Lars & Goobar, Ariel (2004); Cosmology
and Particle Astrophysics, 2nd ed. Springer
Verlag. ISBN 3-540-43128-4.
Branco, G. C., Shafi, Q., & Silva-Marcos,
J. I. (2001). Recent developments in particle
physics and cosmology. Dordrecht: Kluwer Academic.
ISBN 0-7923-7181-X
Collins, P. D. B. (2007). Particle physics
and cosmology. New York: John Wiley & Sons.
ISBN 0-471-12071-5
Kazakov, D. I., & Smadja, G. (2005). Particle
physics and cosmology the interface. NATO
science series, v. 188. Dordecht: Springer.
ISBN 1-4020-3161-0
"Science and technology - Cosmology and particle
physics - What can the matter B?". The Economist
(379, number 8474): 94. 2006. OCLC 102695447.
