We study the mathematics and physics involved in the generation of grav- itational waves by stellar mass binary black holes and their subsequent detection by LISA, a space based interferometer...Show moreWe study the mathematics and physics involved in the generation of grav- itational waves by stellar mass binary black holes and their subsequent detection by LISA, a space based interferometer detector. We show that LISA will be capable of detecting nearby binary black holes with a maxi- mal relative distance error of 0.2 and skylocation error of 1 square degree if the total mass of the binary is at least eighty solar masses.Show less
With the development of next-generation gravitational waves detectors, we aim to measure and infer data on a broader range of the energy and redshift spectrum. However, in this range, deviations...Show moreWith the development of next-generation gravitational waves detectors, we aim to measure and infer data on a broader range of the energy and redshift spectrum. However, in this range, deviations from theories that predict a non-standard propagation speed for GWs are expected to become non negligible anymore. Moreover, it has been shown that the presence of inhomogeneities and structures in our universe does affect the GWs observables: with the forecasted level of precision of future detectors, such corrections can not be ignored. In this work we set in the frame of quartic scalar-tensor theories of gravity to study such relativistic effects with the presence of an extra scalar degree of freedom. Due to the complexity of the full theory, we opted for a phenomenological approach to describe the dispersion relation and amplitude evolution of the metric perturbation. Using this technique, we evaluated the relativistic corrections to frequency and direction of propagation of the GWs wave-vector. On the other hand, it was not possible to analytically calculate the relativistic corrections to the tensor amplitude even using the parametric approach, as a consequence of the elevated number of terms in the amplitude evolution equation. Nevertheless, after selecting from such equation the transverse-traceless modes, we were able to find, using the N-P formalism, which types of term can actually contribute to the evolution of the physical modes.Show less
We study the mathematics and physics involved in the generation of grav- itational waves by stellar mass binary black holes and their subsequent detection by LISA, a space based interferometer...Show moreWe study the mathematics and physics involved in the generation of grav- itational waves by stellar mass binary black holes and their subsequent detection by LISA, a space based interferometer detector. We show that LISA will be capable of detecting nearby binary black holes with a maxi- mal relative distance error of 0.2 and skylocation error of 1 square degree if the total mass of the binary is at least eighty solar masses.Show less
In a time of thriving Gravitational Wave physics, we study Black Hole Quasi-Normal Modes emitted in the post-ringdown phase of merger events. By using Boundary Effective Field Theoretical methods,...Show moreIn a time of thriving Gravitational Wave physics, we study Black Hole Quasi-Normal Modes emitted in the post-ringdown phase of merger events. By using Boundary Effective Field Theoretical methods, we search for modifications to General Relativity in the strong-field limit, for scalar as well as gravitational field perturbations. Going beyond General Relativity, Black Holes are predicted to produce echoing signals, for which we characterise observational parameters, by searching for leading order Boundary Conditions near the Black Hole horizon. For a scalar field, we discuss a parity symmetric and a shift symmetric configuration, while for a gravitational field, parity and diffeomorphism symmetry are implemented. The diffeomorphism symmetric Boundary Condition oddly seems to mix modes. Given the intimate relationship between Effective Field Theory and renormalisation techniques, we also comment on recent first principle arguments that have been brought up regarding the supposed impossibility of echo observation. We find that these arguments over-interpret a regularisation cut-off. From our perspective, the arguments still have merit, but do not form the no-go theorem that it seems to. In the end, only observation can give the decisive answer on the existence of Black Hole echoes.Show less
Einstein’s theory of general relativity provides cosmologists with the current best framework to describe the Universe. Nevertheless, the theory has observational and theoretical limitations. In...Show moreEinstein’s theory of general relativity provides cosmologists with the current best framework to describe the Universe. Nevertheless, the theory has observational and theoretical limitations. In turn, scientists have come to develop modified theories of gravity. The thesis compares the theory of general relativity with a particular class of modified theories called scalar-tensor theories, which incorporates a scalar field that couples to matter. Using f(R) theory, a sub-class of scalar-tensor theories, we develop a theoretical understanding of how certain observational differences emerge from a given gravitational framework. After doing so we use EFTCAMB to simulate various gravitational theories and compute their predicted luminosity distance power spectrum. This tool tracks the variance of the inferred luminosity distance fluctuations emerging from independent gravitational waves and supernova events. The fluctuations arise from the anisotropies present in the Universe, which have their evolution and dynamics directly dependent on the gravitational framework probed. More explicitly, the thesis investigates a general class of effective field theory models, k-Mouflage and Generalised Brans-Dicke models. The interference power spectrum was unique to modified gravitational theories making its detection a smoking gun result for the existence of modified theories. Even so, it remains that the signals present are not substantial enough to be detected in the foreseeable future. More encouragement comes from constructing the gravitational wave luminosity distance power spectrum since it exhibits amplitudes of larger values. Nevertheless, most theories investigated showed small deviations from general relativity, rendering them difficult to constrain in the foreseeable future using this tool as well. From this we conclude that although the luminosity distance power spectrum has the potential to be a revolutionary tool in fundamental physics and cosmology, its use in upcoming surveys to help constrain theories, let alone delineate them, seems to be unrealistic for the foreseeable future.Show less
