Cosmological and Astrophysical Viability of Weyl Gravity

Islam, Tousif (2018) Cosmological and Astrophysical Viability of Weyl Gravity. Masters thesis, Indian Institute of Science Education and Research Kolkata.

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Abstract

In recent times, Weyl Conformal Gravity has gained momentum because of its grounding in field theory, gauge invariant features of the standard model and its interesting cosmology with naturally arising inflation. This thesis explores the viability of conformal gravity as an alternative to general relativity. The work focuses primarily on re-examining the bending of light in Weyl gravity and demonstrates that conformal gravity complies with solar deflection test. Furthermore, the ability of Weyl gravity to explain galactic rotation curves adequately has been tested using available astronomical data. Our study finds the conformal scaling fits to rotation curves to be consistent with the light bending issue. Additionally, we obtain better bounds for conformal gravity parameters ɣ*,ɣ₀ and k. Weyl gravity predicts an eventual decline in rotation curves of galaxies due to global inhomogeneities. Extended rotation curve of the Milky Way has been used to confirm that such predicted decline is indeed in accordance with observation. A detailed study employing the most up-dated mass model of the Milky Way reveals that conformal gravity fit to the rotation curve is comparable to other popular gravity models such as MOG, MOND and GR plus dark matter. The thesis also rejects the recent claim that no gravity model could explain the derived acceleration curve in cluster A1689 and shows that conformal gravity can account for the derived acceleration profile while a different set of conformal parameters well within the range obtained from galactic rotation curve survey is chosen. The work establishes that such acceleration profiles derived from lensing data is extremely sensitive to the specific model of gravity used.

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