Georg Raffelt, Max-Planck-Institut für Physik, München, Germany. Introduction to the. Dark Universe

Transcription

1 Georg Raffelt, Introduction Max-Planck-Institut to the Dark für Universe Physik, München Introduction to the Dark Universe 4 th MPI Young Scientists Workshop July 2005, Ringberg Castle, Tegernsee, Germany

2 Portion of the Hubble Ultra Deep Field Dark Energy 73% (Cosmological Constant) Ordinary Matter 4% (of this only about 10% luminous) Dark Matter 23% Neutrinos 0.1 2%

3 Portion of the Hubble Ultra Deep Field Dark Energy 73% (Cosmological Constant) Ordinary Matter 4% (of this only about 10% luminous) Dark Matter 23% Neutrinos 0.1 2%

4 Baryogenesis in the Early Universe Sakharov conditions for creating the Baryon Asymmetry of the Universe (BAU( BAU) C and CP violation Baryon number violation Deviation from thermal equilibrium Andrei Sakharov Particle-physics standard model Violates C and CP Violates B and L by EW instanton effects (B L conserved) However, electroweak baryogenesis not quantitatively possible within particle-physics physics standard model Works in SUSY models for small range of parameters A.Riotto & M.Trodden: Recent progress in baryogenesis Ann. Rev. Nucl. Part. Sci. 49 (1999) 35

5 Hubble Diagram Supernova Ia as cosmological standard candles Accelerated expansion (Ω M = 0.3, Ω Λ = 0.7) Decelerated expansion (Ω M = 1)

6 Einstein s Greatest Blunder Density of gravitating mass & energy Newton s constant Curvature term is very small or zero (Euclidean spatial geometry) Friedmann equation for Hubble s expansion rate 2 a 8 G k H 2 π N Λ = & = ρ + a 3 2 a 3 Yakov Borisovich Zeldovich Cosmological constant Λ (new constant of nature) allows for a static universe by global anti-gravitation Quantum field theory of elementary particles inevitably implies vacuum fluctuations because of Heisenberg s uncertainty relation, e.g. E and B fields can not simultaneously vanish Ground state (vacuum) provides gravitating energy Vacuum energy ρ vac is equivalent to Λ

7 H vs h-barh

8 Expansion of Different Cosmological Models Cosmic scale factor a Ω M = 0.3 Ω Λ = 0.7 Ω M = 0 Ω M = 1 Ω M > Adapted from Bruno Leibundgut 7 today Time (billion years)

9 Dark Matter in Galaxy Clusters A gravitationally bound system of many particles obeys the virial theorem 2 E kin = E grav 2 mv G M m 2 = N r 2 r 2 v G N M r 1 r Velocity dispersion from Doppler shifts and geometric size Coma Cluster Total Mass

10 Dark Matter in Galaxy Clusters Fritz Zwicky: Die Rotverschiebung von Extragalaktischen Nebeln (The redshift of extragalactic nebulae) Helv.. Phys. Acta 6 (1933) 110 In order to obtain the observed average Doppler effect of 1000 km/s or more, the average density of the Coma cluster would have to be at least 400 times larger than what is found from observations of the luminous matter. Should this be confirmed one would find the surprising result that dark matter is far more abundant than luminous matter.

11 Giant Arc in Cluster Cl z = z = 0.336

12 Giant Arcs Gravitationally Lensed Background Galaxies Distorted image (Partial Einstein ring) Background galaxy A.Tyson, Physics Today, 1992:6, pg.24 Foreground cluster of galaxies Observer

13 Gravitational Lensing in Clusters of Galaxies Galaxy cluster Cl [Hubble Space Telescope] Numerical Simulation

14 Structure of Spiral Galaxies Spiral Galaxy NGC 2997 Spiral Galaxy NGC 891

15 Rotation Curve of the Solar System Kepler s Law v rotation = G M radius Newton central

16 Galactic Rotation Curve from Radio Observations Observed flat rotation curve Expected from luminous matter in the disk Spiral galaxy NGC 3198 overlaid with hydrogen column density [ApJ 295 (1985) 305] Rotation curve of the galaxy NGC 6503 from radio observations of hydrogen motion [MNRAS 249 (1991) 523]

17 Structure of a Spiral Galaxy

18 Structure of a Spiral Galaxy Dark Halo

19 Galaxy Distribution in the Sky

20 Formation of Structure Smooth Structured Structure forms by gravitational instability of primordial density fluctuations

21 Generating the Primordial Density Fluctuations Early phase of exponential expansion (Inflationary epoch) Zero-point fluctuations of quantum fields are stretched and frozen Cosmic density fluctuations are frozen quantum fluctuations

22 A Slice of the Universe Cosmic Stick Man ~ 185 Mpc Galaxy distribution from the CfA redshift survey [ApJ 302 (1986) L1]

23 2dF Galaxy Redshift Survey (15 May 2002) ~ Mpc Mpc 2dF CfA Las Campanas

24 Power Spectrum of Density Fluctuations Field of density fluctuations δρ (x) δ (x) = ρ Fourier transform δ d 3 x e ik x k = δ (x ) Power spectrum essentially square of Fourier transformation δ δ = ( 2 π ) 3ˆ δ ( k k ) P(k ) δ k k δˆδˆ function with the δ-function Power spectrum is Fourier transform of two-point correlation function (x=x( 2 x 1 ) 3 d k (x) (x ) (x ) e ik x ξ = δ 2 δ 1 = P(k) ( 2 ) 3 π dω dk = 4 π k e ik x k 3 P(k) π 2 (k) Gaussian random field (phases of Fourier modes δ k uncorrelated) is fully characterized by the power spectrum 2 P (k) = δ k or equivalently by k P(k) k (k) = = 2 2π 2 δ k 2 π

25 Gravitational Growth of Density Perturbations The dynamical evolution of small perturbations δρ (x) δ ( x) = < < 1 ρ is independent for each Fourier mode δ k For pressureless, nonrelativistic matter (cold dark matter) naively expect exponential growth Only power-law growth in expanding universe Radiation dominates a t 1/2 Matter dominates a t 2/3 Sub-horizon λ H 1 δ k const δ k a t 2/3 Super-horizon λ H 1 δ k a 2 t

26 Processed Power Spectrum in Cold Dark Matter Scenario Primordial spectrum usually assumed to be of power-law form 2 P (k) = δ n k k Harrison-Zeldovich ( flat ) spectrum n = 1 expected from inflation (n may be slightly less than 1, depending on details of inflationary phase) Primordial spectrum Suppressed by stagnation during radiation phase

27 Power Spectrum of Cosmic Density Fluctuations

28 COBE Temperature Map of the Cosmic Microwave Background T = K (uniform on the sky)

29 COBE Temperature Map of the Cosmic Microwave Background T = K (uniform on the sky)

30 COBE Temperature Map of the Cosmic Microwave Background Dynamical range T T = mk ( T/( T/T 10-3 ) Dipole temperature T = K distribution (uniform on from the Doppler sky) effect caused by our motion relative to the cosmic frame

31 COBE Temperature Map of the Cosmic Microwave Background Dynamical Dynamical range range T T T = T = 18 µk K mk ( T/( ( T/( T/T T/T ) -3 ) Dipole temperature T = K distribution (uniform on from the Doppler sky) effect caused by our motion relative to the cosmic frame Primordial temperature fluctuations

32 Last Scattering Surface Here & Now Horizon Θ Redshift z

33 Power Spectrum of CMBR Temperature Fluctuations Sky map of CMBR temperature fluctuations ( ( θ, ϕ ) = T ( θ, ϕ ) T T Multipole expansion l, = = m lm l 0 m l l ( θ ϕ ) = a Y ( θ, ϕ ) Acoustic Peaks Angular power spectrum C l = a l m a l m = 1 2 l + 1 l a m = l l m a l m

34 Flat Universe from CMBR Angular Fluctuations Spergel et al. (WMAP Collaboration) astro-ph/ Triangulation with acoustic peak flat (Euclidean) negative curvature l max 200 Ω tot Ω tot = 1.02 ± 0.02 positive curvature Known physical size of acoustic peak at decoupling (z 1100) Measured angular size today (z = 0)

35 CMBR - The Cosmic Rosetta Stone Power-law index (tilt) n = 1.0, 1.1, 1.2 Hubble constant H 0 = 50, 60, 70 Total density Ω tot = 1.0, 0.5, 0.3 Baryon density Ω B = 5, 7.5, Physics Today 1997:11, 32

36 Concordance Model of Cosmology A Friedmann-Lemaître Lemaître-Robertson-Walker model with the following parameters perfectly describes the global properties of the universe 1 1 Expansion rate H = (72 ± 4) km s Mpc Spatial curvature Age t 9 = (13.7 ± 0.2) 10 years 0 Vacuum energy Ω Λ = 0.73 ± R 1 curv > 5H 0 Ω tot = 1.02 ± Ω Λ Matter Ω M = 0.27 ± Ω Λ + Ω M = 1.02 ± Baryonic matter Ω = B ± The observed large-scale structure and CMBR temperature fluctuations are perfectly accounted for by the gravitational instability mechanism with the above ingredients and a power-law primordial spectrum of adiabatic density fluctuations (curvature fluctuations) P(k) k n Power-law index n = 0.93 ± 0. 03

37 Weakly Interacting Particles as Dark Matter More than 30 years ago, beginnings of the idea of weakly interacting particles (neutrinos) as dark matter Massive neutrinos are no longer a good candidate (hot dark matter) However, the idea of weakly interacting massive particles as dark matter is now standard

38 What is wrong with neutrino dark matter? Galactic Phase Space ( Tremaine Tremaine-Gunn-Limit ) Maximum mass density of a degenerate Fermi gas m 3 ν (mν vescape ) ρ max = m = 3 2 π p 3 max ν π n max m ν > ev m ν > ev Spiral galaxies Dwarf galaxies Neutrino Free Streaming (Collisionless( Phase Mixing) At T < 1 MeV neutrino scattering in early universe ineffective Stream freely until non-relativistic Wash out density contrasts on small scales Neutrinos Over-density Neutrinos Nus are Hot Dark Matter Ruled out by structure formation

39 Formation of Structure Smooth Structured

40 Formation of Structure Smooth Structured A fraction of hot dark matter suppresses small-scale scale structure

41 Neutrino Free Streaming Transfer Function Power suppression for λ FS 100 Mpc/h Σm ν Σm ν = 0 = 0.3 ev Σm ν = 1 ev Transfer function P(k) = T(k) P 0 (k) Effect of neutrino free streaming on small scales T(k) = 1 8Ω ν /Ω M valid for 8Ω ν /Ω M 1 Hannestad, Neutrinos in Cosmology, hep-ph/ ph/

42 Recent Cosmological Limits on Neutrino Masses Authors Spergel et al. (WMAP) 2003 [astro-ph/ ] Hannestad 2003 [astro-ph/ ] Tegmark et al [astro-ph/ ] Barger et al [hep-ph/ ] ph/ ] Crotty et al [hep-ph/ ] ph/ ] Hannestad 2004 [hep-ph/ ] ph/ ] Seljak et al [astro-ph/ ] Σm ν /ev (limit 95%CL) Data / Priors 0.69 WMAP, CMB, 2dF, σ 8, HST 1.01 WMAP, CMB, 2dF, HST 1.8 WMAP, SDSS 0.75 WMAP, CMB, 2dF, SDSS, HST WMAP, CMB, 2dF, SDSS & HST, SN WMAP, SDSS, SN Ia gold sample, Ly-α data from Keck sample WMAP, SDSS, Bias, Ly-α data from SDSS sample

43 Lee-Weinberg Weinberg-Curve For m ν 1 MeV neutrinos freeze out nonrelativistically Density suppressed by annihilation before freeze-out Weakly interacting massive particles (WIMPs) possible as cold dark matter

44 Supersymmetric Extension of Particle Physics In supersymmetric extensions of the particle-physics physics standard model, every boson has a fermionic partner and vice versa Spin Standard particle 1/2 Leptons (e, ν e, ) Quarks (u, d, ) Superpartner Sleptons (e, ~ ν ~ e, ) Squarks (u, ~ ~ d, ) Spin 0 1 Gluons W ± Z 0 Photon (γ)( 0 2 Higgs Graviton Gluinos Wino Zino Photino (γ) ~ Higgsino Gravitino 1/2 1/2 3/2 If R-Parity R is conserved, the lightest SUSY-particle (LSP) is stable Most plausible candidate for dark matter is the neutralino, similar to a massive Majorana neutrino Neutralino = C Photino 1 + C 2 Zino + C 3 Higgsino

45 The Search for Dark Matter in our Galaxy (With permission of David Simmonds ) Direct search experiments exist for WIMPs (Weakly Interacting Massive Particles, often assumed to be supersymmetric neutralinos) Axions (Very low-mass very weakly interacting bosons, motivated by CP problem of QCD)

46 Search for Neutralino Dark Matter Direct Method (Laboratory Experiments) Galactic dark matter particle (e.g.neutralino) Crystal Recoil energy (few kev) is measured by Energy Ionisation deposition Scintillation Cryogenic

47 Direct Detection Methods

48 Direct Detection Experiments

49 CRESST Experiment to Search for Dark Matter

50 One of the CRESST Detector Crystals

51 DAMA Evidence for WIMP Detection DAMA experiment in Gran Sasso (NaI scintillation detector) observes an annual modulation at a 6.3σ statistical CL, based on 110 ton-days of data [Riv. N. Cim. 26 (2003) 1 73] 1 Annual modulation of WIMP signal a smoking gun signature Time (day) Detector stability? Background stability?

52 Limits from WIMP Search Experiments DAMA claimed detection Paolo Gondolo et al. Expectation from supersymmetric models astro-ph/

53 Projected WIMP Sensitivities

54 Search for Neutralino Dark Matter Direct Method (Laboratory Experiments) Galactic dark matter particle (e.g.neutralino) Crystal Recoil energy (few kev) is measured by Energy Ionisation deposition Scintillation Cryogenic Indirect Method (Neutrino Telescopes) Galactic dark matter particles are accreted Annihilation Sun High-energy neutrinos (GeV-TeV) can be measured

55 High-Energy Neutrino Telescopes Antares Project Nestor Project Baikal 200 PMTs Amanda II, 800 PMTs IceCube Project

56 Muon Flux from WIMP Annihilation in the Sun Need a km 3 water Cherenkov detector to reach solar background

57 Can We See the Dark Matter? GLAST Project HESS airshower telescope, Namibia Dark matter particles can directly annihilate χχ γγ The dark halo of our galaxy can slightly glow in high-energy gamma rays MAGIC airshower telescope, La Palma

58 Some Dark Matter Candidates Supersymmetric particles Neutralinos Axinos Gravitinos Little Higgs models Gauge hierarchy problem Axions CP Problem of strong interactions Kaluza-Klein Klein excitations Mirror matter Sterile neutrinos Wimpzillas (superheavy particles) MeV-mass dark matter Q-balls Primordial black holes Large extra dimensions Exact parity symmetry Right-handes handes states should exist Super GZK cosmic rays Explain cosmic-ray positrons Why not?

59 Portion of the Hubble Ultra Deep Field (Dennis the Menace used by permission of Hank Ketcham and North America Syndicate)