M.Sc Student | Naim Shim'on |
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Subject | Interaction between a Cluster and a Galaxy Under f (R) Gravity |

Department | Department of Physics |

Supervisor | Professor Adi Nusser |

Full Thesis text |

English Abstract Cosmological observations of standard candle supernovae and the cosmic microwave background show that the expansion of the Universe is accelerating in the last ~8 Gyr. General relativity, with standard model fields and dark matter as the only sources for the stress-energy tensor, does not predict this acceleration. A straightforward solution is the addition of a cosmological constant to the Einstein field equations. A generalization of this idea is to replace the linear dependence of GR on the Ricci curvature, R, with a non-linear function f(R).

English Abstract In this thesis we address consequences of f(R) on a system of a galaxy in the vicinity of a rich cluster of galaxies. The solutions are obtained by a numerical solver written specifically for this purpose. The solutions are derived for the Hu-Sawicki version of f(R) gravity, which is designed to agree with Solar System constraints. The gravitational force which emerges from f(R) gravity deviates from GR at the level of up to 30% within the cluster. The interaction with a nearby galaxy modulates this deviation up to 150% at the outskirts of the galaxy. The deviations are proportional to the galaxy mass and strongly dependent on the cluster-galaxy separation, such that those dependencies can be used in order to constrain f(R). Furthermore, f(R) gravity generates tidal torques on the galaxy which can be stronger than the Newtonian tidal torque by two orders of magnitude. These tidal torques may