AY 101 Lecture Notes - Lecture 32: Flatness Problem, Isotropy, Cosmic Microwave Background
Document Summary
Evolution of a big-bang universe, the cosmic microwave, background radiation, large-scale. Four disti(cid:374)(cid:272)t for(cid:272)es of (cid:374)ature (cid:862)freeze out(cid:863) Particle era: matter/ antimatter particle pairs condense. Symmetry breaking leaves a universe made mostly of matter. Era of nuclei: universe opaque like inside of a star. Era of atoms: atoms form and universe becomes transparent. Era of galaxies: stars and galaxies form. Pair production: in early universe, particles condensed out of the gamma radiation from the primordial fireball. Two gamma rays interact and spontaneously condense into a pair of matter-antimatter particles. The particles could be an electron and antielectron, or a proton and antiproton. The anti-particle has the opposite charge of the regular particle. Matter and antimatter cannot coexist for long. If a matter particle encounters its anti- parti(cid:272)le, the(cid:455) disi(cid:374)tegrate ea(cid:272)h other (cid:271)a(cid:272)k i(cid:374)to ga(cid:373)(cid:373)a ra(cid:455)s. this is (cid:272)alled (cid:862)(cid:373)atter- a(cid:374)ti(cid:373)atter a(cid:374)(cid:374)ihilatio(cid:374)(cid:863) Initially, pair production is a symmetric process because it produces equal amounts of matter and antimatter.
