Baryon Asymmetry: Why is Matter More Abundant?

[spidey]

Its said that matter is more abundant than antimatter in observable universe and hence comes the baryon asymmetry...but why matter and antimatter should be equal in amount...which law governs this?

 

[astrorob]

Matter "condensed" out of radiation (think radiation era). We know two colliding photons will pair produce given the correct energy to produce a particle and its corresponding anti-particle - this would yield exactly similar quantities for antimatter and matter from the standard model.