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Cosmology II: The CMB, dark matter and dark energy Ruth Durrer Département de Physique Théorique et CAP Université de Genève Suisse CERN Summer school July 26, 2017 Ruth Durrer (Université de Genève) Cosmology II July 26, 2017 1 / 23 Contents 1 Recombination 2 The cosmic microwave background 3 Dark matter 4 Dark energy models 5 Conclusions Ruth Durrer (Université de Genève) Cosmology II July 26, 2017 2 / 23 Nucleosyhthesis (the formation of Helium, Deuterium, ...) Inflation ? Thermal history In the past the Universe was not only much denser than today but also much hotter. The most remarkable events of the hot Universe: Recombination (electrons and protons combine to neutral hydrogen). Age of the Universe: t0 13:7 billion years ' Ruth Durrer (Université de Genève) Cosmology II July 26, 2017 3 / 23 Inflation ? Thermal history In the past the Universe was not only much denser than today but also much hotter. The most remarkable events of the hot Universe: Recombination (electrons and protons combine to neutral hydrogen). Nucleosyhthesis (the formation of Helium, Deuterium, ...) Age of the Universe: t0 13:7 billion years ' Ruth Durrer (Université de Genève) Cosmology II July 26, 2017 3 / 23 Thermal history In the past the Universe was not only much denser than today but also much hotter. The most remarkable events of the hot Universe: Recombination (electrons and protons combine to neutral hydrogen). Nucleosyhthesis (the formation of Helium, Deuterium, ...) Inflation ? Age of the Universe: t0 13:7 billion years ' Ruth Durrer (Université de Genève) Cosmology II July 26, 2017 3 / 23 At T 3000K (z 1100, t 3000000years) the Universe is ’cold’ enough that protons' and electrons∼ can combine' to neutral hydrogen. After this, photons no longer scatter with matter but propagate freely. Their energy (and hence the temperature) is redshifted to T0 = 2:728K today, corresponding to a density of about 400 photons per cm3. This cosmic microwave background can be observed today in the (1– 400)GHz range. It has a perfect blackbody spectrum. It represents a ’photo’ of the Universe when it was about 300’000 years young, corresponding to a redshift of z 1100. ' Recombination 4 4 4 Since the photon (radiation) energy density scales like T a− (z + 1) while 3 3 / / the matter density scales like mn a− (z + 1) , at very early time, the Universe is radiation dominated (z/> 3000,/ t < 104 years). ∼ ∼ Ruth Durrer (Université de Genève) Cosmology II July 26, 2017 4 / 23 After this, photons no longer scatter with matter but propagate freely. Their energy (and hence the temperature) is redshifted to T0 = 2:728K today, corresponding to a density of about 400 photons per cm3. This cosmic microwave background can be observed today in the (1– 400)GHz range. It has a perfect blackbody spectrum. It represents a ’photo’ of the Universe when it was about 300’000 years young, corresponding to a redshift of z 1100. ' Recombination 4 4 4 Since the photon (radiation) energy density scales like T a− (z + 1) while 3 3 / / the matter density scales like mn a− (z + 1) , at very early time, the Universe is radiation dominated (z/> 3000,/ t < 104 years). ∼ ∼ At T 3000K (z 1100, t 3000000years) the Universe is ’cold’ enough that protons' and electrons∼ can combine' to neutral hydrogen. Ruth Durrer (Université de Genève) Cosmology II July 26, 2017 4 / 23 This cosmic microwave background can be observed today in the (1– 400)GHz range. It has a perfect blackbody spectrum. It represents a ’photo’ of the Universe when it was about 300’000 years young, corresponding to a redshift of z 1100. ' Recombination 4 4 4 Since the photon (radiation) energy density scales like T a− (z + 1) while 3 3 / / the matter density scales like mn a− (z + 1) , at very early time, the Universe is radiation dominated (z/> 3000,/ t < 104 years). ∼ ∼ At T 3000K (z 1100, t 3000000years) the Universe is ’cold’ enough that protons' and electrons∼ can combine' to neutral hydrogen. After this, photons no longer scatter with matter but propagate freely. Their energy (and hence the temperature) is redshifted to T0 = 2:728K today, corresponding to a density of about 400 photons per cm3. Ruth Durrer (Université de Genève) Cosmology II July 26, 2017 4 / 23 It represents a ’photo’ of the Universe when it was about 300’000 years young, corresponding to a redshift of z 1100. ' Recombination 4 4 4 Since the photon (radiation) energy density scales like T a− (z + 1) while 3 3 / / the matter density scales like mn a− (z + 1) , at very early time, the Universe is radiation dominated (z/> 3000,/ t < 104 years). ∼ ∼ At T 3000K (z 1100, t 3000000years) the Universe is ’cold’ enough that protons' and electrons∼ can combine' to neutral hydrogen. After this, photons no longer scatter with matter but propagate freely. Their energy (and hence the temperature) is redshifted to T0 = 2:728K today, corresponding to a density of about 400 photons per cm3. This cosmic microwave background can be observed today in the (1– 400)GHz range. It has a perfect blackbody spectrum. Ruth Durrer (Université de Genève) Cosmology II July 26, 2017 4 / 23 Recombination 4 4 4 Since the photon (radiation) energy density scales like T a− (z + 1) while 3 3 / / the matter density scales like mn a− (z + 1) , at very early time, the Universe is radiation dominated (z/> 3000,/ t < 104 years). ∼ ∼ At T 3000K (z 1100, t 3000000years) the Universe is ’cold’ enough that protons' and electrons∼ can combine' to neutral hydrogen. After this, photons no longer scatter with matter but propagate freely. Their energy (and hence the temperature) is redshifted to T0 = 2:728K today, corresponding to a density of about 400 photons per cm3. This cosmic microwave background can be observed today in the (1– 400)GHz range. It has a perfect blackbody spectrum. It represents a ’photo’ of the Universe when it was about 300’000 years young, corresponding to a redshift of z 1100. ' Ruth Durrer (Université de Genève) Cosmology II July 26, 2017 4 / 23 The cosmic microwave background: the spectrum (Fixen et al. 1996) Nobel Prize 1978 for Penzias and Wilson, Nobel Prize 2006 for Mather o T0 = 2:728K 270:5 C ' − Ruth Durrer (Université de Genève) Cosmology II July 26, 2017 5 / 23 Subtracting the monopole a dipole 3 of amplitude 10− becomes vis- ible. It is mainly∼ due to the motion of the solar system with respect of the sphere of emission (last scatter- ing surface). And what is this? Left over after subtracting the dipole. Fluctuations 5 of amplitude 10− . ∼ The cosmic microwave background: anisotropies Map of the CMB temperature: perfectly isotropic. SmootRuth Durrer et al. (Université (1999), de Genève) Nobel Prize 2006 Cosmology II July 26, 2017 6 / 23 And what is this? Left over after subtracting the dipole. Fluctuations 5 of amplitude 10− . ∼ The cosmic microwave background: anisotropies Map of the CMB temperature: perfectly isotropic. Subtracting the monopole a dipole 3 of amplitude 10− becomes vis- ible. It is mainly∼ due to the motion of the solar system with respect of the sphere of emission (last scatter- ing surface). SmootRuth Durrer et al. (Université (1999), de Genève) Nobel Prize 2006 Cosmology II July 26, 2017 6 / 23 The cosmic microwave background: anisotropies Map of the CMB temperature: perfectly isotropic. Subtracting the monopole a dipole 3 of amplitude 10− becomes vis- ible. It is mainly∼ due to the motion of the solar system with respect of the sphere of emission (last scatter- ing surface). And what is this? Left over after subtracting the dipole. Fluctuations 5 of amplitude 10− . ∼ SmootRuth Durrer et al. (Université (1999), de Genève) Nobel Prize 2006 Cosmology II July 26, 2017 6 / 23 The cosmic microwave background: anisotropies ESA/Planck (2015) Ruth Durrer (Université de Genève) Cosmology II July 26, 2017 7 / 23 The cosmic microwavePlanck Collaboration: background: Cosmological parameters anisotropies 6000 5000 ∆T ] 4000 2 (n) = a`mY`m(n) K T µ [ 3000 X 2 TT C` = a`m D 2000 hj j i `(` + 1) ` = C` 1000 D 2π 0 600 60 300 30 TT 0 0 ∆T D 5 2 10− ∆ -300 -30 T ' × -600 -60 2 10 30 500 1000 1500 2000 2500 ESA/Planck (2015) Fig. 1. The Planck 2015 temperature power spectrum. At multipoles ` 30 weo show the maximum likelihood frequency averaged o ` = 200 corresponds to about≥ 1 . ’acoustic’ peaks. (θ 180 =`) temperature spectrum computed from the Plik cross-half-mission likelihood with) foreground and other nuisance parameters deter-' mined from the(This MCMC is analysis roughly of the base the⇤CDM double cosmology. of In the the multipole angular range size 2 ` of29, the we plot full the power moon spectrum (or of the sun).) estimates from the Commander component-separation algorithm computed over 94% of the sky. The best-fit base ⇤CDM theoretical spectrum fitted to the Planck TT+lowP likelihood is plotted in the upper panel. Residuals with respect to this model are shown in the lower panel. The error bars show 1 σ uncertainties. ± sults to theRuth likelihood Durrer (Université methodology de byGenève) developing several in- the full “TT,TE,EE”Cosmology likelihoods) II would di↵er in any substantive July 26, 2017 8 / 23 dependent analysis pipelines. Some of these are described in way had we chosen to use the CamSpec likelihood in place of Planck Collaboration XI (2015). The most highly developed of Plik. The overall shifts of parameters between the Plik 2015 these are the CamSpec and revised Plik pipelines. For the likelihood and the published 2013 nominal mission parameters 2015 Planck papers, the Plik pipeline was chosen as the base- are summarized in column 7 of Table 1.
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