Matter/Anti-Matter Asymmetry

The above illustrates pair production and pair annihilation

The figure shows annihilation and pair production in a bubble chamber.

In the early Universe, matter is created via pair production and destroyed by annihilation. Since an equal amount of matter and anti-matter is produced in pair production (at least based on simple theories), there could be a problem.

The problem is more than a little vexing because the asymmetry is small.

The ratio of photons to matter particles is then

This is a huge number; note that

There must have been 1,000,000,000 and 1 electrons for every 1,000,000,000 positrons in the early Universe. If an asymmetry at this level did not exist, then we would not be here.

The small matter/anti-matter asymmetry is another mystery of the Universe which we can either simply accept or try to explain

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