1. Cosmology, 2010 1 1 Cosmology I & II Fall 2010

2. Cosmology, 20102 Cosmology I & II  Cosmology I: 7.9.-22.10.  Cosmology II: 1.11.-17.12.  http://theory.physics.helsinki.fi/~cosmology http://theory.physics.helsinki.fi/  Lectures in A315, Mon & Tue 14.15-16.00  Syksy Räsänen, C326, syksy.rasanen@iki.fi  Exercises in D112, Fri 14.15-16.00 (starting 17.9.)  Stanislav Rusak, A314, stanislav.rusak@helsinki.fi  Exercises form 20% of the score, the exam 80%  Exercises are handed out on Monday, and returned by following Monday.  Exception: next week they are due on Wednesday.  Cosmology I: 7.9.-22.10.  Cosmology II: 1.11.-17.12.  http://theory.physics.helsinki.fi/~cosmology http://theory.physics.helsinki.fi/  Lectures in A315, Mon & Tue 14.15-16.00  Syksy Räsänen, C326, syksy.rasanen@iki.fi  Exercises in D112, Fri 14.15-16.00 (starting 17.9.)  Stanislav Rusak, A314, stanislav.rusak@helsinki.fi  Exercises form 20% of the score, the exam 80%  Exercises are handed out on Monday, and returned by following Monday.  Exception: next week they are due on Wednesday.

3. Cosmology, 20103 Cosmology I  Introduction  Basics of general relativity  Friedmann-Robertson-Walker (FRW) models  Thermal history of the universe  Big Bang nucleosynthesis (BBN)  Dark matter  Introduction  Basics of general relativity  Friedmann-Robertson-Walker (FRW) models  Thermal history of the universe  Big Bang nucleosynthesis (BBN)  Dark matter

4. Cosmology, 20104 Cosmology II  Quantum field theory (QFT) for children  Inflation  Structure formation  Brief introduction to perturbation theory  Cosmic microwave background (CMB) anisotropy  Quantum field theory (QFT) for children  Inflation  Structure formation  Brief introduction to perturbation theory  Cosmic microwave background (CMB) anisotropy

5. Cosmology, 20105 Observations: basics  Electromagnetic radiation  Radio waves  Microwaves  IR  Visible light  UV  X-Rays  Gamma rays  Massive particles  Cosmic rays (protons, antiprotons, heavy ions, electrons, antielectrons)  Neutrinos  Gravity waves?  Composition of the solar system  Electromagnetic radiation  Radio waves  Microwaves  IR  Visible light  UV  X-Rays  Gamma rays  Massive particles  Cosmic rays (protons, antiprotons, heavy ions, electrons, antielectrons)  Neutrinos  Gravity waves?  Composition of the solar system

6. Cosmology, 20106 Observations in practice  Motion of galaxies  Distribution of galaxies (large scale structure)  Abundances of light elements  Cosmic microwave background  Luminosities of distant supernovae  Number counts of galaxy clusters  Deformation of galaxy images (cosmic shear) ...  Motion of galaxies  Distribution of galaxies (large scale structure)  Abundances of light elements  Cosmic microwave background  Luminosities of distant supernovae  Number counts of galaxy clusters  Deformation of galaxy images (cosmic shear) ...

7. Cosmology, 20107 Laws of physics  General relativity  Quantum quantum field theory  Atomic physics, nuclear physics, the Standard Model of particle physics  Statistical physics and thermodynamics  General relativity  Quantum quantum field theory  Atomic physics, nuclear physics, the Standard Model of particle physics  Statistical physics and thermodynamics

8. Cosmology, 20108 Homogeneity and isotropy: observations http://map.gsfc.nasa.gov/media/101080/index.html

9. Cosmology, 20109 Homogeneity and isotropy: observations http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=47333

10. Cosmology, 201010 Homogeneity and isotropy: observations arXiv:astro-ph/0604561, Nature 440:1137.2006

11. Cosmology, 201011 Homogeneity and isotropy: observations

12. Cosmology, 201012 Homogeneity and isotropy: theory  The observed statistical homogeneity and isotropy motivates theory with exact H&I  The Friedmann-Robertson-Walker models  The expansion of the universe is described by the scale factor a(t)  Extrapolating the known laws of physics we find that 14 billion years ago a → 0, ρ → ∞, T → ∞  The observed statistical homogeneity and isotropy motivates theory with exact H&I  The Friedmann-Robertson-Walker models  The expansion of the universe is described by the scale factor a(t)  Extrapolating the known laws of physics we find that 14 billion years ago a → 0, ρ → ∞, T → ∞

13. Cosmology, 201013 The Big Bang  The early universe was  Hot  Dense  Rapidly expanding  H&I and thermal equilibrium ⇒ easy to calculate  High T ⇒ high energy ⇒ quantum field theory  The early universe was  Hot  Dense  Rapidly expanding  H&I and thermal equilibrium ⇒ easy to calculate  High T ⇒ high energy ⇒ quantum field theory

14. Cosmology, 201014 Timeline of the universe 10 -12 s 10 -6 s 1 s 1 h TeV GeV MeV Electroweak (EW) transition Fermions, W +,W -,Z 0 become massive g massless Baryogenesis? QCD phase transition: quarks  p, n ν decoupling e + e - annihilation n/p ≈ 1/6 Big bang nucleosynthesis (BBN) 2 H, 3 He, 4 He, 7 Li

15. Cosmology, 201015 Short history of the universe 1 yr 10 6 yr 10 10 yr Now keV eV meV Decoupling of light and baryons => atoms The universe becomes transparent Cosmic Microwave background (CMB) Structure formation Formation of galaxies, first stars Dark ages

16. Cosmology, 201016 Short history of the universe 10 -42 s 10 19 GeV Planck time GUT era? Baryogenesis? Topological defects formed? (monopoles, cosmic strings, domain walls) Supersymmetry breaks? 10 -36 s 10 -30 s 10 -12 s 10 -24 s 10 -18 s 10 15 10 12 10 9 10 18 10 6 10 3 GeV Inflation? SU(3)  SU(2)  U(1)

17. Cosmology, 201017 Structure formation  CMB shows the initial conditions  The early universe is exactly homogeneous up to small perturbations of 10 -5 to 10 -3  Seeds of structure  Gravity is attractive ⇒ fluctuations grow into galaxies, clusters of galaxies, filaments, walls and voids, which form the large-scale structure of the universe  CMB shows the initial conditions  The early universe is exactly homogeneous up to small perturbations of 10 -5 to 10 -3  Seeds of structure  Gravity is attractive ⇒ fluctuations grow into galaxies, clusters of galaxies, filaments, walls and voids, which form the large-scale structure of the universe

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21. Cosmology, 201021 Structure formation  Origin of fluctuations: inflation  A period of acceleration in the early universe  Quantum fluctuations are stretched by the fast expansion and frozen in place  Growth of fluctuations  Due to ordinary gravity  Depends on the initial state plus the matter composition  Baryonic matter is too smoothly distributed at last scattering  Origin of fluctuations: inflation  A period of acceleration in the early universe  Quantum fluctuations are stretched by the fast expansion and frozen in place  Growth of fluctuations  Due to ordinary gravity  Depends on the initial state plus the matter composition  Baryonic matter is too smoothly distributed at last scattering

22. Cosmology, 201022 Dark matter  Luminous matter: stars, gas (plasma), dust  Large-scale structure, CMB anisotropies, motions of stars in galaxies, galaxies and gas in clusters, gravitational lensing, BBN,... ⇒ there is invisible matter  Baryonic matter: cold and hot gas, brown dwarfs  However, the majority of matter (about 80%) is non-baryonic, either cold dark matter (CDM) or warm dark matter (WDM, m > 10 keV)  Neutralinos, technicolor dark matter, right- handed neutrinos,...  Luminous matter: stars, gas (plasma), dust  Large-scale structure, CMB anisotropies, motions of stars in galaxies, galaxies and gas in clusters, gravitational lensing, BBN,... ⇒ there is invisible matter  Baryonic matter: cold and hot gas, brown dwarfs  However, the majority of matter (about 80%) is non-baryonic, either cold dark matter (CDM) or warm dark matter (WDM, m > 10 keV)  Neutralinos, technicolor dark matter, right- handed neutrinos,...

23. Cosmology, 201023 Dark energy  Exactly homogeneous and isotropic models with baryonic and dark matter don’t quite agree with the observations  Measured distances are longer by a factor of 1.4-1.7 and the expansion is faster than predicted by a factor of 1.5-2  Three possibilities:  1) There is matter with negative pressure which makes the universe expand faster (dark energy)  2) General relativity does not hold (modified gravity)  3) The homogeneous and isotropic approximation is not good enough  Exactly homogeneous and isotropic models with baryonic and dark matter don’t quite agree with the observations  Measured distances are longer by a factor of 1.4-1.7 and the expansion is faster than predicted by a factor of 1.5-2  Three possibilities:  1) There is matter with negative pressure which makes the universe expand faster (dark energy)  2) General relativity does not hold (modified gravity)  3) The homogeneous and isotropic approximation is not good enough

24. Cosmology, 201024 Dark energy  Dark energy is the preferred option  Dark energy  has large negative pressure  is smoothly distributed  has an energy density about three times that of baryonic plus dark matter  The most natural candidate is vacuum energy  “The greatest mystery in physics.”  Dark energy is the preferred option  Dark energy  has large negative pressure  is smoothly distributed  has an energy density about three times that of baryonic plus dark matter  The most natural candidate is vacuum energy  “The greatest mystery in physics.”