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i. Dark matter
ii. Dark Energy
Distribution of matter
Dark matter models
Candidates of dark matter
Nature of dark matter
ii. Internal structure
Over 65 years ago in 1933 the Swiss astrophysicist Fritz Zwicky was the first
to infer the existence of unseen matter, (dark matte)
An undetected form of mass that emits /absorb no light but whose
existence we infer from its gravitational influence.
An unknown form of energy that seems to be the source of a
repulsive force causing the expansion of the universe to
IN 1998 the Hubble Space Telescope
(HST) observations show that universe
Due to strange kind
of energy-fluid that filled space
Maybe there is something wrong
with Einstein's theory of gravity
1929 Edwin Hubble plotted redshift against relative distance, he found that the
redshift of distant galaxies increased as a linear function of their distance. The
only explanation for this observation is that the universe was expanding.
Does dark matter really exist ?
In 1991, the COBE satellite team announced the successful detection of these
fluctuations, confirming the existence of dark matter
The cosmic background radiation results recently published by the team of
scientists analyzing the observations of the WMAP satellite are generally
assessed as providing a brilliant and comprehensive verification of the
What might dark matter be made of ?
MACHOS or WIMPS
Dead or failed stars in
halos of galaxies (brown
white dwarfs, small black
it has been long thought that dark matter could be explained by an as
weakly interacting elementary particle, a ‘‘WIMP
Dark matter models :
Age of universe: 13.8 Gyr (billion years)
Dark Energy: 74%
Dark Matter: 22%
But from gravitational effects it’s more than 4% of the total energy density
Super symmetric standard model (MSSM) is a particularly popular variant
provide a suitable dark-matter candidate in the form of neutralino
THE FAVORED CANDIDATES FOR DARK MATTER
For over a decade, the favored candidates for dark matter have been
hypothetical elementary particles that are
long-lived → lifetime 14 billion years
cold → particles are non-relativistic
collision less → interaction between dark matter particles negligible
it has been known for nearly 20 years that light neutrinos (hot relativistic) must
be a negligible
Neutralino. These particles are electrically neutral and weakly interacting
ideal candidates for WIMPs.
Axion. A very light neutral particle (with mass of order 1 μeV ) It interacts
through such a tiny force that it is never in thermal equilibrium, so the
explanation for its abundance is not as simple
Why Cold, collionless dark particles ?
There are three main reasons
Numerical simulations of structure formation with cold, collisionless dark
matter agree with most observations of structure
For a special subclass known as WIMPs (weakly interacting massive
particles), there is a natural explanation for why they have the requisite
Specific appealing candidates for the dark matter particles in models of
As concordance model, is mathematically quite specific it can be tested at many
different physical scales.
Large scale. Thousands of megaparsecs (Mpc) – one parsec is 3.26 light-years,
a kiloparsec (kpc) is one thousand parsecs and an Mpc is one million parsecs)
are seen in the CBR itself .
According to this dark matter must be
Smaller scale.( from one Mpc down to the scale of galaxies, kpc, and below )
results of the tests are uncertain or disagreement with theoretical data
‘‘WIMP is still a leading candidate
ALTERNATIVES TO COLD, COLLISIONLESS DARK MATTER
Possible disagreement between theory and observation on small scale have
provide new proposals for the nature of dark matter .
Strongly Self-Interacting dark matter . hypothetical form of dark
matter consisting of particles with strong self-interactions
Warm dark matter. Dark matter may be born with a small velocity dispersion
which leaves it now with only perhaps 100 m/s velocity but which can have a
significant effect on small scale structure
Repulsive dark matter. may consist of a condensate of massive bosons with
a short range repulsive potential
Fuzzy dark matter. Dark matter could take the form of ultra-light scalar
particles cannot be concentrated on smaller scales, resulting is softer cores
and reduce small-scale structure
Massive black hole. If dark matter consist of black holes then
several dynamical mysteries concerning the properties of our galaxy could be
NATURE OF DARK MATTER
Time of formation for objects of a given mass M (as measured at formation) for
structures with increasing mass (dwarf, low surface brightness (LSB), ordinary
(L*) galaxies and galaxy clusters) for different models of dark matter.
How the number of objects of a given type depends on their mass (as
observed today) for different dark matter models.
How the density density of the inner one kiloparsec depends on the mass of
the system for different dark matter models
How the number of dwarfs in (1 Mpc)3 volume depends on the average
density within that volume
Astrophysical observations tell us that we live in a dark-dominated universe
We have worked under the assumption that.
Recent results from collider physics, astrophysics, and cosmology encourage
broader thinking in regards to possible
dark-matter candidates—dark-matter need not be made exclusively of ‘WIMPs
Facilities dedicated to nuclear physics are well-positioned to investigate certain
non-WIMP models, and we have discussed the models which are probed at such
facilities in some detail
we conclude that a bright future exists for the discovery of things dark.
Dark matter studies entrain nuclear physics
Susan Gardner a,∗, George M. Fuller b
a Department of Physics and Astronomy, University of Kentucky, Lexington,
KY 40506-0055, USA
b Department of Physics, University of California, San Diego, La Jolla, CA
New Light on Dark Matter
Jeremiah P. Ostriker1,2 and Paul Steinhardt2