the dark side of the universe: dark energy and dark matter harutyun khachatryan center for cosmology...
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The dark side of the Universe: dark energy and dark matter
Harutyun Khachatryan
Center for Cosmology and Astrophysics
Content of the Universe after Planck
Density proportion evolution
Lambda chronology
2013 Planck, density content revision
Cosmological modelsFriedmann-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
Friedmann equations
Energy-momentum tensor
Omega budget
Luminosity distance
dark energy 0.69
matter density 0.31
radiation density 10^-4
For concordance model for flat universe
Cosmological constant
Λ?Einstein equations 1916
Einstein 1917
Dark energy 1998Hubble diagram
2011 Nobel Prize in Physics
Extragalactic Distance ladder
Astrophysical parametersL luminosity, total energy emitted by an object per second.
m apparent magnitude, observed brightness.
M absolute magnitude, calibrated brightness.
M=m-5(log10(DL)-1)
Standard candlesClassical Cepheids Type Ia
Supernovae
Cepheid light curve
Type Ia Supernovae
Crab nebula
1054 A.D. supernova remnant
SN Ia light curve
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.
Hubble’s or Lemaitre’s law?
Lemaitre 1927 Hubble 1929
Hubble diagram indicating accelerated expansion
Riess et al. 1998
Higher redshifts: gamma-ray burstersz=1-10 and more (arguable)emits in few seconds as much as the Sun
during its lifetimenature unknown, some empirical relations
exit
Can they be used for the Hubble diagram?
Calibrating GRBs Empirical relations
H. J. M. Cuesta…..H. G. Khachatryan,.. A&A, 2008
Amati relation
lag versus luminosity relation
variability versus luminosity relation
Vacuum fluctuations Zeldovich 1967
Cosmic coincidence
Equation of state, w
Dark energy summaryNegative pressure, p=-ρΩ=0.69Equation of state, cosmological constant w=-
1Various models: vacuum fluctuations,
General Relativity extensions (scalar field coupled, Chern-Simons, f(R), etc), quintessence, holography…
Slide by A.Taylor, Motivating EUCLID space mission, 2011
Dark matter chronology1932- Jan Oort, stellar motion in the local
galactic neighbourhood
1933- Fritz Zwicky, motion in clusters of galaxies
1970- Vera Rubin, galaxy rotation curves
Virial theorem
2<T>=Vtot
Zwicky, F., Helvetica Physica Act 6 (1933)
Coma clusterDark matter
M31 rotation curve
V.C. Rubin & W.K. Ford 1970
Galaxy rotation curves
Gravitational lensing
Einstein 1912,1936
Bullet cluster
1E 0657-558
Bullet cluster X-ray image
Modified Newtonian dynamics
MOND theory (by Milgrom)MOND acceleration related to the Newtonian acceleration aN
at weak acceleration limit of gravity
interpolation function
Dark matter summary Ω=0.27Particle candidates: axion, WIMPs, neutrino
(small part), supersymmetric particles…Models: cold dark matter, warm dark matter,
hot dark matterMOND
Challenge to homogeneity of the Universe?
Greatest cosmic structure
73 quasar cluster
z=1.27, longest dimension 1240 Mpc, mean length 500 Mpc
R. Clowes et al. MN, 2013
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…).