Gravitational waves and cosmology.

Abstract

The recent discovery of GW140915 and the confirmation of the existence of gravitational waves (GWs) has garnered the attention of many physicists as they seek to understand their behavior as they travel across the universe. In this dissertation, one will find the study singularities which may arise in plane GWs, and cosmological perturbations may affect GWs as they propagate through an expanding, inhomogeneous universe. It is found that in the BJR coordinates, singularities arise at the focused point u = us, except in the two cases: (i) α = 1/2, ∀ χn, and (ii) α = 1, χi = 0, where χn are the coefficients in the expansion and α is a parameter. When observing GWs produced from remote astrophysical sources, one finds that there are three scales to consider, λ, Lc, and L which denote the typical wavelength of the GW, the scale of the cosmological perturbations, and the size of the observable universe, respectively. The Einstein equations were calculated for GWs on the cosmic scale, and the geometric optics approximation found the gravitational integrated Sachs-Wolfe effects created by both the cosmological scalar and tensor perturbations.