Sakharov conditions

The three conditions identified by Andrei Sakharov for generating a net excess of baryons over antibaryons from an initially symmetric universe: baryon-number violation, C and CP violation, and departure from thermal equilibrium.

Baryon number: A quantum number that counts baryons minus antibaryons in a physical system. Its violation lets processes change the net baryon count from zero.
Andrei Sakharov: A Soviet physicist who proposed the three conditions for producing the universe's baryon asymmetry in 1967. He first formulated the conditions and argued that baryon nonconservation could occur in the early universe.
Electroweak baryogenesis: A proposed origin of the baryon asymmetry involving electroweak-era processes in the early universe. It attempts to satisfy all three conditions using electroweak physics.
Baryon-to-photon ratio: The ratio of baryon number density to photon number density in the universe. It quantifies the small relic asymmetry any successful mechanism must reproduce.
Electroweak phase transition strength: The thermodynamic character and strength of the early universe's electroweak transition. The Standard Model transition is not strong enough to provide the required nonequilibrium conditions.
Charge conjugation: A transformation that replaces each particle with its antiparticle and reverses additive internal charges. Violating this symmetry helps distinguish matter-producing reactions from antimatter-producing ones.
Baryon asymmetry of the universe: The observed excess of matter over antimatter, expressed as a nonzero cosmic baryon abundance. This unexplained imbalance motivated Sakharov's conditions.
Grand unified theory baryogenesis: Baryogenesis scenarios in which interactions at grand-unification energies violate baryon number. Heavy particles in these models can provide baryon-violating reactions and CP asymmetries.
Proton decay: A hypothetical decay of a proton into lighter particles that violates baryon number. Some theories that enable baryogenesis also predict proton decay, which experiments constrain.
Lepton number: An additive quantum number that distinguishes leptons from antileptons. Its violation could generate the initial asymmetry in leptogenesis scenarios.

Linked from 9 pages