What CP violation means — charge-parity symmetry is broken in weak interactions, explaining matter-antimatter asymmetry

What the strong CP problem is — why does QCD not violate CP symmetry when it has no reason not to

The strong CP problem questions why CP violation isn't observed in Quantum Chromodynamics despite theoretical possibility

What CPT symmetry is — the combination of charge, parity, and time reversal is always conserved

CP-symmetry implies charge, parity, and time reversal conservation

What the Dirac equation predicted — relativistic quantum mechanics requires antimatter to exist

Dirac equation predicted the existence of antimatter in relativistic quantum mechanics

Why the Dirac equation has negative energy solutions — interpreted as positrons, confirmed by Anderson in 1932

Dirac equation predicts negative energy states, later identified as antiparticles, positrons, by Anderson's experiments

What spontaneous symmetry breaking does — the vacuum state breaks a symmetry that the laws possess

Vacuum state in quantum field theory breaks global U(1) gauge symmetry

Which gauge symmetry underlies the unification of the electromagnetic, weak, and strong forces at high energies, and how does it manifest in the Standard Model?

SU(2)xSU(3) gauge symmetry unifies forces in the Standard Model, manifesting as weak and strong interactions