Neutron Star Models in Alternative Theories of Gravity

Abstract

OF THE DISSERTATION Neutron Star Models in Alternative Theories of Gravity by Dimitrios Manolidis Doctor of Philosophy in Physics Washington University in St. Louis, 2014 Professor Clifford M. Will, Chair We study the structure of neutron stars in a broad class of alternative theories of gravity. In particular, we focus on Scalar-Tensor theories and f(R) theories of gravity. We construct static and slowly rotating numerical star models for a set of equations of state, including a polytropic model and more realistic equations of state motivated by nuclear physics. Observable quantities such as masses, radii, etc are calculated for a set of parameters of the theories. Specifically for Scalar-Tensor theories, we also calculate the sensitivities of the mass and moment of inertia of the models to variations in the asymptotic value of the scalar field at infinity. These quantities enter post-Newtonian equations of motion and gravitational waveforms of two body systems that are used for gravitational-wave parameter estimation, in order to test these theories against observations. The construction of numerical models of neutron stars in f(R) theories of gravity has been difficult in the past. Using a new formalism by Jaime, Patino and Salgado we were able to construct models with high interior pressure, namely pc > ρc/3, both for constant density models and models with a polytropic equation of state. Thus, we have shown that xi earlier objections to f(R) theories on the basis of the inability to construct viable neutron star models are unfounded.