The Matter-Antimatter Asymmetry Problem

The core problem: Current theories suggest the Big Bang should have created equal amounts of matter and antimatter, which would have completely annihilated. Yet we observe a universe dominated by matter.

Why Matter Survived

There must have been a tiny asymmetry in the early universe:

• For every 1 billion matter-antimatter annihilation events
• Approximately 1 extra matter particle survived
• This residual matter forms everything we see today

Sakharov's Conditions

Physicist Andrei Sakharov (1967) established three requirements for baryogenesis:

• Baryon Number Violation: Processes that change net matter content
• C/CP Symmetry Violation:
  • C-violation: Particle processes differ from antiparticle processes
  • CP-violation: Observed in kaon and B-meson decays (but insufficient in Standard Model)
• Thermal Non-Equilibrium: Universe must depart from equilibrium during critical phase transitions

Evidence for Matter Dominance

• No significant primordial antimatter observed in:
  • Cosmic rays
  • Distant galaxies
  • Cosmic microwave background
• Photon-to-baryon ratio: ~1,000,000,000:1 (residual from annihilation)

Current Scientific Status

This remains an unsolved mystery in physics:

• Sakharov's conditions are necessary but not sufficient
• Observed CP-violation in Standard Model is 10 orders of magnitude too small
• Ongoing research areas:
  • Neutrino properties (leptogenesis)
  • Supersymmetry models
  • Axion cosmology
  • Primordial black hole effects

Conclusion: The survival of matter requires physics beyond the Standard Model. Resolving this baryogenesis problem would revolutionize our understanding of fundamental physics.

Key experiments: LHC (CERN), Super-Kamiokande (Japan), DUNE (Fermilab), CMB-S4 telescopes