Download presentation
Presentation is loading. Please wait.
Published byMolly Long Modified over 9 years ago
1
The dark side of the Universe: dark energy and dark matter Harutyun Khachatryan Center for Cosmology and Astrophysics
2
Content of the Universe after Planck
3
Density proportion evolution
4
Lambda chronology 2013 Planck, density content revision
5
Cosmological models Friedmann-Robertson-Walker metric Continuity equation Evolution equation Spatial curvature K=0 flat (Minkowski), K=+1 positive curvature(sphere) K=-1 negative curvature spectral redshift cosmic redshift
6
Friedmann equations
7
Energy-momentum tensor
8
Omega budget
9
Luminosity distance dark energy 0.69 matter density 0.31 radiation density 10^-4 For concordance model for flat universe
10
Cosmological constant Λ?Λ? Einstein equations 1916 Einstein 1917
11
Dark energy 1998 Hubble diagram
12
2011 Nobel Prize in Physics
13
Extragalactic Distance ladder
14
Astrophysical parameters L luminosity, total energy emitted by an object per second. m apparent magnitude, observed brightness. M absolute magnitude, calibrated brightness. M=m-5(log 10 (D L )-1)
15
Standard candles Classical Cepheids Type Ia Supernovae
16
Cepheid light curve
17
Type Ia Supernovae
18
Crab nebula 1054 A.D. supernova remnant
19
SN Ia light curve
20
Hubble’s law V = H r V- velocity of the galaxy, r- distance to the galaxy, Hubble’s constant H = 69.32 ± 0.80 (km/s)/Mpc (after Planck). V=H(r)r Observations: Hubble redshift-distance law of galaxies Theory: from FRW metric follows for small distances, z << 1.
21
Hubble’s or Lemaitre’s law? Lemaitre 1927 Hubble 1929
22
Hubble diagram indicating accelerated expansion Riess et al. 1998
23
Higher redshifts: gamma-ray bursters z=1-10 and more (arguable) emits in few seconds as much as the Sun during its lifetime nature unknown, some empirical relations exit Can they be used for the Hubble diagram?
24
Calibrating GRBs Empirical relations H. J. M. Cuesta…..H. G. Khachatryan,.. A&A, 2008 Amati relation lag versus luminosity relation variability versus luminosity relation
26
Vacuum fluctuations Zeldovich 1967
27
Cosmic coincidence
28
Equation of state, w
29
Dark energy summary Negative pressure, p=-ρ Ω=0.69 Equation of state, cosmological constant w=-1 Various models: vacuum fluctuations, General Relativity extensions (scalar field coupled, Chern- Simons, f(R), etc), quintessence, holography…
30
Slide by A.Taylor, Motivating EUCLID space mission, 2011
31
Dark matter chronology 1932- Jan Oort, stellar motion in the local galactic neighbourhood 1933- Fritz Zwicky, motion in clusters of galaxies 1970- Vera Rubin, galaxy rotation curves
32
Virial theorem 2 =V tot Zwicky, F., Helvetica Physica Act 6 (1933) Coma cluster Dark matter
33
M31 rotation curve V.C. Rubin & W.K. Ford 1970
34
Galaxy rotation curves
35
Gravitational lensing Einstein 1912,1936
36
Bullet cluster 1E 0657-558
37
Bullet cluster X-ray image
38
Modified Newtonian dynamics
39
MOND theory (by Milgrom) MOND acceleration related to the Newtonian acceleration a N at weak acceleration limit of gravity interpolation function
40
Dark matter summary Ω=0.27 Particle candidates: axion, WIMPs, neutrino (small part), supersymmetric particles… Models: cold dark matter, warm dark matter, hot dark matter MOND
41
Challenge to homogeneity of the Universe? Greatest cosmic structure
42
73 quasar cluster z=1.27, longest dimension 1240 Mpc, mean length 500 Mpc R. Clowes et al. MN, 2013
43
Conclusions Modern cosmology passed to the precision cosmology era. Dark energy: favored, cosmological constant w=-1. The nature unknown. Dark matter: many candidates, none favored. The nature unknown. Challenges to the concordance model (CMB low multipole anomaly, alignments, non- Gaussianities…).
Similar presentations
© 2025 SlidePlayer.com. Inc.
All rights reserved.