Brief review of cosmology Universe is expanding
Δλ/λ ∝ d
Hubble's law (1929):
v = H d Edwin Powell Hubble (1889 -1953)
the first observa onal evidence of Big Bang theory Big Bang
• 1927
Georges Lemaître (1894 – 1966) • Einstein general rela vity • homogeneous and isotropic
universe Alexander Friedman • (cosmological principle) (1888 – 1925) • Friedmann's equa ons - descrip on of the universe from the Big Bang onwards • Fred Hoyle – 1949
Sir Fred Hoyle (1915 - 2001) universe is isotropic and homogeneous in space and me
• 1964 – Arno Penzias and Robert Wilson – discovery of Cosmic Microwave Background radia on – CMB – with T=2.725 K
• distribu on and evolu on of galaxies Big Bang nucleosynthesis
• Alpher-Bethe-Gamow • predicts quan ty of 4He, 3He, 2H in 7Li with respect to 1H
• dependance on η=nB/nγ ← CMB ⇒ mass % • 75% H • 25% 4He, (~) • ~ 10−4 2H, (OK) • ~ 10−4 3He • ~ 10−10 7Li, 7Be (2x) 1. beginning to infla on – Planck epoch: 0-10-43 s, T~ 1034 K - gravita on decouples GUT 10-38 s – strong interac on decouples→ huge amount of energy released → Infla on: grows in size by a factor of 1035
2. electroweak epoch: 10-38 to 10-10 s phase transi on, soup of elementary par cles: photons, gluons, quarks weak and EM interac on decouple 3. par cle epoch: 10-10 to 1 s quarks and an quarks annihilate symmetry breaking → residual quarks→ ma er
Hadron epoch: from 10-6 to 10-5 s, T~ 1015 K: quarks → hadrons unstable decay, p and n remain Lepton epoch: most leptons and an leptons → annihila on → residual leptons 4. from 1 to 100 s - n ↔ p + e + νe + -(m_n-m_p)/kT n + e ↔ p + νe nn/np =e - n + νe ↔ p + e at T~ 10 GK stops: nn/np =0.223 neutrons: β decay with τ=617 s 5. 3 - 20 min when T decreases to ~ 1 GK deuterons are produced: 2 p+n ↔ 1H+γ ra o p:n at the end: np:nn=7:1 → nHe:nH=1:12 or. mHe:m=0.25
2 n + p → 1H + γ.
2 3 2 3 1H + n → H + γ in 1H + p → He + γ. Finally, 4He is produced: 2 2 4 3 4 1H + 1H → He + γ, He + n → He + γ and 3H + p → 4He + γ. atomic nuclei: most n bound in He, very li le in Lithium, Beryllium, Deuterium nuclei • no elements > Be • because no stable nuclei with A=5 or 8 (see triple alpha process) • Universe con nues expanding
• comparisson with observa ons: • WMAP • 10.000 years: end of radia on era, beginning of ma er dominated era • 380.000 years: T~3000 K – atoms form, ma er and radia on dcouple – universe becomes transparent→ CMB • >400 Myr: forma on of stars, galaxies, planets...