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The Study of Kinematic Dipole and Clustering Dipole Magnitudes using Large-Scale Structure Data and the Effects of Modified Gravity

Tadayyoni, Haniyeh Sadat | 2024

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 57498 (04)
  4. University: Sharif University of Technology
  5. Department: Physics
  6. Advisor(s): Baghram, Shant; Rahvar, Sohrab
  7. Abstract:
  8. The dipole in the angular distribution of the cosmic microwave background (CMB) is typically attributed to the Doppler effect and our motion relative to the CMB rest frame. It is expected that observations of large-scale structures (LSS) would also exhibit a related kinematic dipole, helping to confirm the kinematic origin of the CMB dipole. However, numerous studies of the LSS dipole have shown significant discrepancies with predictions based on the CMB. In this study, we assume that the CMB dipole is due to our motion relative to the CMB frame, and using radio source data from NVSS, we calculate the dipole induced by local large-scale structures across different redshift ranges. Furthermore, the correlation between these two dipoles (kinematic and clustering) is computed across various redshift intervals in both linear and nonlinear regimes, using the one-loop and halo models. We find that the impact of the clustering dipole is significant in the redshift ranges 0.025 < z < 3.14 and 0.01 < z < 3, relative to the kinematic dipole. Additionally, in the redshift range 0.025 < z < 3.14, the correlation between the two dipoles becomes substantial. Furthermore, we investigate these results within the framework of modified gravity theories, specifically f(R) and DGP gravity models. By examining these models, it is possible to better understand how the cosmic dark energy component affects the dipole. Finally, by comparing these three models, we can see that the f(R) model predicts a higher clustering dipole compared to the standard cosmological model, and the standard cosmological model shows better agreement with observational data than DGP model, which explains the discrepancy between the kinetic and clustering dipoles and leads to a higher dipole amplitude
  9. Keywords:
  10. Cosmic Microwave Background (CMB) ; Cosmology Standard Model ; Universe Large-Scale Structure ; Generalized Gravity ; Clustering Dipole ; Cosmological Principle ; Kinematic Dipole

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