Introduction to Cosmology

Electroweak Interactions 121 Universe are not and will never be in thermal equilibrium on a cosmic timescale. This result permit ...

122 Thermal History of the Universe Protons and anti-protons have electromagnetic interactions similar to positrons and electron ...

Electroweak Interactions 123 Weak leptonic reactions are e±+ (−) 휈e→e±+ (−) 휈e, (6.34) (−) 휈e+ (−) 휈e→ (−) 휈e+ (−) 휈e, (6.35) wh ...

124 Thermal History of the Universe For each species of relativistic fermions participating in the thermal equilibrium there is ...

Electroweak Interactions 125 Temperature and Time Scales. Let us now derive a relation between the temper- ature scale and the t ...

126 Thermal History of the Universe hadrons, forming a dense medium ofquark matter. Below the transition the quarks become bound ...

Electroweak Interactions 127 At this time the number density of nucleons decreases quickly because they have become nonrelativis ...

128 Thermal History of the Universe Also, the muons decay fast compared with the age of the Universe, with a lifetime of 2.2μs, ...

Photon and Lepton Decoupling 129 The condition for a given species of particle to remain in thermal equilibrium is then that the ...

130 Thermal History of the Universe a constant, except at the thresholds where particle species decouple. The physical meaning o ...

Photon and Lepton Decoupling 131 γ e A vμ vτ ve B Figure 6.3A system of communicating vessels illustrating particles in thermal ...

132 Thermal History of the Universe The density parameter is 훺휈=^3 11 푁훾 휌cℎ^2 ∑ 푖 푚푖. (6.68) Recombination Era. As long as ther ...

Photon and Lepton Decoupling 133 streaming photons from this era form the CMB radiation and their point of last contact with mat ...

134 Thermal History of the Universe Saha prediction. Consequently, all the times predicted by this nonequilibrium analysis diffe ...

Big Bang Nucleosynthesis 135 At energies of the order of푚n−푚p= 1 .293MeV or less, this ratio is dominated by the exponential. Th ...

136 Thermal History of the Universe favored on energetic grounds already at 2MeV, free nucleons continue to be favored by the hi ...

Big Bang Nucleosynthesis 137 the exponential factor in Equation (6.73). The neutrons also decay into protons by beta decay, n→e− ...

138 Thermal History of the Universe was stable in comparison with the age of the universe. At퐴=8 the nuclei^8 Band^8 Li have lif ...

Big Bang Nucleosynthesis 139 instructive to follow the arguments about how they affect the value of푌 4. Let us rewrite the decou ...

140 Thermal History of the Universe The^3 He isotope can be seen in galactic star-forming regions containing ionized hydrogen (H ...