07/14/2022
By Ananya Mukherjee
The Physics and Applied Physics Department invites you to a Master's Defense:
Candidate Name: Ananya Mukherjee
Defense Date: Tuesday, July 19, 2022
Time: 1 to 2 p.m.
Location: Via Zoom
Thesis Title: Linear Growth of Structure in Massive Gravity
Advisor: Nishant Agarwal, Department of Physics and Applied Physics, University of Massachusetts Lowell
Committee Members:
- Viktor Podolskiy, Department of Physics and Applied Physics, University of Massachusetts Lowell
- Timothy Cook, Department of Physics and Applied Physics, University of Massachusetts Lowell
Abstract: We study background dynamics and the growth of matter perturbations in the extended quasi-dilaton setup of massive gravity. For the analysis of perturbations, we first choose a scalar field matter component and obtain the conditions under which all scalar perturbations are stable. We work in unitary gauge for the matter field, which allows us to directly map to known results in the limit of general relativity.
By performing a parameter search, we find that the perturbations are unstable in general, while a particular choice of potential, where the scalar field effectively behaves like pressureless matter, allows for stable perturbations. We next consider the growth of matter perturbations in a cold dark matter-dominated Universe. Working in conformal Newtonian gauge, we obtain evolution equations for various observables including the growth factor and growth rate, and find scale-independent growth in the quasi-static and sub-horizon approximations. We finally show how the Hubble parameter and matter perturbations evolve in massive gravity for a specific choice of parameter values, and how this evolution compares to the standard cosmological model consisting of a cosmological constant and cold dark matter.