matter-antimatter asymmetry

matter–antimatter asymmetry

The asymmetry between matter and antimatter in the Universe; i.e. the fact that all the matter in the Universe appears to be in the form of matter rather than an equal mixture of matter and antimatter, as might be expected from relativistic quantum mechanics. The problem of explaining this asymmetry is a major challenge for cosmology. Sakharov's conditions provide a general explanation for how this asymmetry can arise. These conditions were implemented in the context of grand unified theories in the late 1970s to provide an explanation of matter–antimatter asymmetry but it is not known whether this explanation is correct.