Searching for gravitational waves produced by cosmic strings in LIGO-Virgo data

This thesis shows the results of the search for gravitational-wave signals produced by cosmic strings using the data from the first two observation runs of the second generation detectors Advanced LIGO and Advanced Virgo. Cosmic strings are one-dimensional topological defects created in the primordial Universe. These objects are predicted by many models of very high energy physics. The gravitational wave signal emitted by cosmic strings is predicted by theory. A matched-filter analysis is used to search for the presence of a signal in Advanced LIGO and Advanced Virgo data. This technique is optimal if the detector noise is Gaussian and stationary, which is not the case. An essential part of the thesis work was to understand and reduce the background noise analysis. This work on data quality has increased the sensitivity of the search. Furthermore, we have shown that the search for transient signals of gravitational waves produced by cosmic strings is limited by the presence of a particular family of noises that mimic the predicted signal for cosmic strings. In the absence of detection, we have placed constraints on the parameters which characterize a cosmic string network for different theoretical models, in order to specify the conditions of their existence. (author)