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Primordial Black Holes as Dark Matter

Rahimi, Maryam | 2017

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 50255 (04)
  4. University: Sharif University of Technology
  5. Department: Physics
  6. Advisor(s): Baghram, Shant
  7. Abstract:
  8. The existance of Dark Matter (DM)has been proved by cosmological and astronomical observation. Yet, all the evidences are based on gravitational effects. It is plausible that DM has a gravitational nature. Any creature with a pure gravitational essence has a chance to bea DM candidate. Primordial Black holes are formed from the density perturbations that are induced by the quantum fluctuations of the vaccum during the inflationary expansion. It is probable that these creatures are the solution of DM problem. By holding the power spectrum that generates the abundance of PBH with the one resulting from observation based on the presumed inflationary model in common, considering the constraints on the power spectrum, the the PBH mass spectrum will be constrained in each wavelength.on the other hand, there is some constraints on PBH mass spectrum in different mass ranges by astronomical and cosmological observation related to evaporation and gravitational effects of PBH on the cosmos. So that one can calculate the abundance of PBH for the mass ranges that there are weak or no constraints on, using the presumed power spectrum and search for the suitable PBH mass range and the suitable form of power spectrum and the probable inflation model underlying, that lead to sufficient amount of PBH production to support all the DM needed. Since in the open windows of PBH mass spectrum constraints, the power spectrum resulting from single scalar field inflation, allowed by CMB and other constraints, it is impossible to produce the needed PBH for DM, one can search for the models that have greater power amplitude on the constraint free ranges of the power spectrum, which are on small scales. In order to prove the inflation model and the power spectrum qualified for producing the sufficient amount of PBH, there are no observation evidence, other than GW detection, which will be possible in the future, if not currently. In this research, we have reviewed the formalisms so as to calculating the PBH abundance, as well as the observational constraints on its abundance. Also we reviewed the possibility of escaping from power spectrum constraint by using inflation models that break the scale invariance and produce amplified scalar perturbations in small scales, in order to produce all of the dark matter in PBH form. We also discussed the possibility of PBH detection, by detection of gravitational waves relating to the PBHs
  9. Keywords:
  10. Dark Matter ; Primordial Black Holes ; Abandance Calculation ; Primordial Black Hole (PBH) Detection by CWs

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