The Sakharov conditions are three fundamental criteria proposed by physicist Andrei Sakharov in 1967 to explain how the early universe could have produced more matter than antimatter, a process known as baryogenesis.
These conditions are necessary for generating the observed matter-antimatter asymmetry in the universe:
- Baryon Number Violation:
There must be processes that do not conserve the number of baryons (particles like protons and neutrons). Without this, the net amount of matter and antimatter would remain equal. - C and CP Symmetry Violation:
The laws of physics must distinguish between particles and antiparticles. C-symmetry (charge conjugation) flips particles to antiparticles, and CP-symmetry flips both charge and parity (spatial reflection). Violations of these symmetries allow reactions to slightly favor the production of matter over antimatter. - Departure from Thermal Equilibrium:
The universe must go through periods where conditions are not in thermal balance. In equilibrium, matter and antimatter would remain in equal amounts, but out-of-equilibrium processes can allow asymmetries to become permanent.
These conditions provide a framework for many theoretical models of baryogenesis, although the exact mechanism is still unknown. Verifying how these conditions were satisfied in the early universe remains a major goal of modern cosmology and particle physics.