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Nov 24
2009
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As the Universe expands and cools and the process of creation and
annihilation of matter/anti-matter pairs slows down. Soon matter and
anti-matter has time to undergo other nuclear processes, such as nuclear
decay. Many exotic particles, massive bosons or mesons, can undergo
decay into smaller particles. If the Universe is out of equilibrium,
then the decay process, fixed by the emergent 
laws of Nature, can
become out of balance if there exists some asymmetry in the rules of
particle interactions. This would result in the production of extra
matter particles, rather than equal numbers of matter and
anti-matter.
In the quantum world, there are large numbers of symmetric relationships. For example, there is the symmetry between matter and anti-matter. For every matter particle, there is a corresponding anti-matter particle of opposite charge. In the 1960's, it was found that some types of particles did not conserve left or right-handedness during their decay into other particles. This property, called parity, was found to be broken in a small number of interactions at the same time the charge symmetry was also broken and became known as CP violation.
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The symmetry is restored when particle interactions are considered under
the global CPT rule (charge - parity - time reversal), which states that
that a particle and its anti-particle may be different, but will behave
the same in a mirror-reflected, time-reversed study. During the
inflation era, the rapid expansion of spacetime would have thrown the T
in CPT symmetry out of balance, and the CP violation would have produced
a small asymmetry in the baryon number.
This is another example of how quantum effects can be magnified to produce large consequences in the macroscopic world. CP violation, by itself, is not sufficient to resolve the matter/anti-matter assymetry. However, it is an example of what may be a class of reactions that produce more matter than anti-matter. The sum of these reactions explains the baryon number. |
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