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

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

CP violation allows for matter dominance over antimatter in the universe

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 QCD (quantum chromodynamics) describes — the strong force between quarks mediated by gluons

QCD describes the strong force interactions between quarks via gluon exchange

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

How does the concept of quark confinement in quantum chromodynamics support the idea that free quarks have never been observed due to the presence of a color force, which causes them to be bound within hadrons?

Quark confinement in QCD implies unobserved free quarks due to color force binding them in hadrons

What the Goldstone theorem says — every spontaneously broken continuous symmetry produces a massless boson

Goldstone theorem: Spontaneously broken continuous symmetries yield massless Goldstone bosons