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Changing the Dynamics of Late Time Universe to Reconcile the Hubble Tension and Cosmological Large Scale Structure Observations

Sheikhansari, Parinaz | 2022

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 55135 (04)
  4. University: Sharif University of Technology
  5. Department: Physics
  6. Advisor(s): Baghram, Shant
  7. Abstract:
  8. The standard cosmological model has been successful in describing many observations from widely different epochs of the Universe, from primordial nucleosynthesis to the accelerat- ing expansion of the present day. With the improvement of the number and the accuracy of observations, some inconsistencies among key cosmological parameters of the model have emerged. Many alternative models are proposed in order to alleviate these tensions. Pecu- liar velocities, the deviation from the regular Hubble flow of the galaxies, are an excellent probe of large-scale structure universe. In a ΛCDM universe, peculiar velocities can be mea- sured using linear perturbation theory, which in known as bulkflow. Recent Observations of bulkflows show higher values than expected in ΛCDM and this contradicts assumption of isotropy and homogenity of the universe. In this work, we used linear perturbation theory to measure bulkflow and fσ8 parameter in two alternative cosmological models, üΛCDM and XCDM . We compared measured bulkflows with ΛCDM predictions and some observation to see which model is preferred by data. We find that üΛCDM model predicts higher bulkflows and is more consistent with observational data but does not reduce σ8 tension. On the other hand, bulkflows measured in XCDM model are lower compared to ΛCDM values however, this model can reconcile σ8 tension
  9. Keywords:
  10. Cosmology ; Structure Formation ; Peculiar Velocity ; Cosmological Perturbations ; Cosmology Standard Model ; Linear Perturbation Theory

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