 Solution

Baryogenesis dynamically creates a baryon–antibaryon imbalance rather than assuming it as an initial condition. Under the usual local relativistic assumptions, the Sakharov conditions are baryon-number violation, C and CP violation, and departure from thermal equilibrium. Without the last condition, inverse reactions and equilibrium constraints cancel a net asymmetry; CP-conjugate rates must differ in a channel with the required number violation.

In heavy-boson decay baryogenesis, heavy particles decay through baryon-violating channels with CP-asymmetric branching. Expansion makes decays/inverse decays fall out of equilibrium; washout reactions must then become ineffective. Inflation would dilute an earlier asymmetry, so the generation/reheating history matters.

In leptogenesis, out-of-equilibrium Majorana-neutrino decays first produce lepton number. Electroweak sphalerons violate $B+L$ while preserving $B-L$ and convert part of the surviving asymmetry to baryon number. In the minimal Standard Model chemical-equilibrium limit, $B=28(B-L)/79$; the coefficient depends on particle content and equilibrated interactions. Electroweak baryogenesis is another possibility if CP violation and a sufficiently strong nonequilibrium phase transition are supplied. The Standard Model's observed parameters do not by themselves furnish an adequate conventional electroweak scenario. Each proposal must quantitatively match the relic asymmetry and avoid washout.