Baryon asymmetry

The baryon asymmetry of particle physics is the observed large dominance of matter over antimatter in the universe. It is one of the most important yet understood phenomena of particle physics, since it can not be explained by the standard model.

The baryon asymmetry is determined by


  • The number of baryons as a measure of the quantity of matter
  • The number of antibaryons ( the antiparticle of the baryons ) as a measure of the amount of antimatter
  • The number of photons.

The observed value

Baryon asymmetry in the universe

The amount of antimatter in the universe can not be determined directly, since they can not be distinguished from matter by astronomers. With the annihilation of matter and antimatter, however, occurs a characteristic electromagnetic radiation that could be but never observed. This means that if large amounts of antimatter in space vorkämen this on large scales of the areas in which matter dominated - would be like on Earth, the solar system and the Milky Way separated. However, this can be largely excluded by the cosmological models.

Theories of production

Previously, it was generally assumed that the baryon asymmetry is an initial condition for our universe that would be predefined at the time of the Big Bang. Since the baryon asymmetry would, however, greatly reduced in the course of inflation, the initial asymmetry would be even also been unnaturally large.

Today the speculative theories of baryogenesis and leptogenesis, which previously could not be verified experimentally say, a dynamic generation of the asymmetry in the Big Bang before.