In physical cosmology, assuming that nature
is described by a Grand Unified Theory, the
grand unification epoch was the period in
the evolution of the early universe following
the Planck epoch, starting at about 10−43
seconds after the Big Bang, in which the temperature
of the universe was comparable to the characteristic
temperatures of grand unified theories.
If the grand unification energy is taken to
be 1015 GeV, this corresponds to temperatures
higher than 1027 K.
During this period, three of the four fundamental
interactions—electromagnetism, the strong
interaction, and the weak interaction—were
unified as the electronuclear force.
Gravity had separated from the electronuclear
force at the end of the Planck era.
During the grand unification epoch, physical
characteristics such as mass, charge, flavour
and colour charge were meaningless.
The grand unification epoch ended at approximately
10−36 seconds after the Big Bang.
At this point several key events took place.
The strong force separated from the other
fundamental forces.
It is possible that some part of this decay
process violated the conservation of baryon
number and gave rise to a small excess of
matter over antimatter (see baryogenesis).
This phase transition is also thought to have
triggered the process of cosmic inflation
that dominated the development of the universe
during the following inflationary epoch.
== See also ==
Chronology of the Universe
Big Bang
