DARK MATTERDark Energy

CONTENTS:

Introductioni. Dark matterii. Dark Energy Distribution of matter Dark matter models Candidates of dark

matteri. Fevered ii. Appealing Physical scalei. Largeii. Small Nature of dark matteri. Demographyii. Internal structure Conclusion

Dark matter: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 whoseexistence we infer from its gravitational influence.

Contents of Universe (by Mass)

.

The true mass distribution of galaxies

DARK ENERGY

An unknown form of energy that seems to be the source of arepulsive force causing the expansion of the universe toaccelerate

IN 1998 the Hubble Space Telescope (HST) observations show that universe is expanding

Due to strange kind of energy-fluid that filled space

Maybe there is something wrong with Einstein's theory of gravity

Expanding Universe

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 concordance model

.

What might dark matter be made of ?

MACHOS or WIMPS

MassiveCompactHaloObjectsDead or failed stars in thehalos of galaxies (brown dwarfs,white dwarfs, small black holes)

WeaklyInteractingMassiveParticlesMysteriousneutrino-likeparticles.

it has been long thought that dark matter could be explained by an as weakly interacting elementary particle, a ‘‘WIMP

Dark matter models :

standard model: 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

Supersymmetric models

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

Appealing candidate

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 abundance

Specific appealing candidates for the dark matter particles in models of fundamental physics

Physical scales

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 beStableColdCollision lessSmaller 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-interactionsWarm 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 thenseveral dynamical mysteries concerning the properties of our galaxy could be better understood

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.

Demography

How the density density of the inner one kiloparsec depends on the mass of the system for different dark matter models

Internal structure:

Environment

How the number of dwarfs in (1 Mpc)3 volume depends on the average density within that volume

CONCLUSION

Astrophysical observations tell us that we live in a dark-dominated universeWe have worked under the assumption that.

Recent results from collider physics, astrophysics, and cosmology encourage broader thinking in regards to possibledark-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 physicsSusan Gardner a,∗, George M. Fuller ba Department of Physics and Astronomy, University of Kentucky, Lexington, KY 40506-0055, USAb Department of Physics, University of California, San Diego, La Jolla, CA 92093, USA

New Light on Dark Matter Jeremiah P. Ostriker1,2 and Paul Steinhardt2