Dark matter


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Dark matter

  1. 1. DARK MATTER Dark Energy
  2. 2. CONTENTS:  Introduction i. Dark matter ii. Dark Energy  Distribution of matter  Dark matter models  Candidates of dark matter i. Fevered ii. Appealing  Physical scale i. Large ii. Small  Nature of dark matter i. Demography ii. Internal structure  Conclusion
  3. 3. 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 whose existence we infer from its gravitational influence.
  4. 4. Contents of Universe (by Mass) .
  5. 5. The true mass distribution of galaxies
  6. 6. DARK ENERGY An unknown form of energy that seems to be the source of a repulsive force causing the expansion of the universe to accelerate 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
  7. 7. 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.
  8. 8. 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
  9. 9. . What might dark matter be made of ? MACHOS or WIMPS Massive Compact Halo Objects Dead or failed stars in the halos of galaxies (brown dwarfs, white dwarfs, small black holes) Weakly Interacting Massive Particles Mysterious neutrino-like particles. it has been long thought that dark matter could be explained by an as weakly interacting elementary particle, a ‘‘WIMP
  10. 10. 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
  11. 11. 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
  12. 12. 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
  13. 13. 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 be Stable Cold Collision less 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
  14. 14. 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 better understood
  15. 15. 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.
  16. 16. How the number of objects of a given type depends on their mass (as observed today) for different dark matter models. Demography
  17. 17. How the density density of the inner one kiloparsec depends on the mass of the system for different dark matter models Internal structure:
  18. 18. Environment How the number of dwarfs in (1 Mpc)3 volume depends on the average density within that volume
  19. 19. 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.
  20. 20. 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 92093, USA New Light on Dark Matter Jeremiah P. Ostriker1,2 and Paul Steinhardt2