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Baryon asymmetry

Baryon asymmetry refers to the observation that apparently there is matter in the Universe but not much antimatter. We don't see galaxies made of antimatter or observe gamma rays that would be produced if large chunks of antimatter would annihilate with matter. Hence at early times, when both were present, there must have been a little bit more matter than antimatter. This is quantified using the asymmetry parameter

$\eta = \frac{n_{baryon} - n_{antibaryon}}{n_{photon}}$

From cosmological measurements such as WMAP,

$\eta \approx (6 \pm 0.25) \times 10^{-10}$

However, the source of baryon asymmetry is said to be one of the Big Problems of Physics.

What is currently the state of the art regarding this puzzle? What's the best fit we can get from the Standard Model? What do we get from lattice simulations?

  • $\begingroup$ Possibly duplicate: physics.stackexchange.com/q/24042/2451 $\endgroup$
    – Qmechanic
    Commented Oct 14, 2012 at 18:29
  • $\begingroup$ Definitely a duplicate, one of these was automatically moved here when the other Physics SE site was killed off. (I posted to both back then to get both research and layman level answers.) $\endgroup$ Commented Oct 14, 2012 at 18:48


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