Interazione di onde gravitazionali con strutture su grande scala

This thesis focuses on the investigation of two intriguing phenomena related to gravitational waves (GWs). The first aspect of our research centers around the novel effect of producing matter density perturbations from the GWs energy density fluctuations and the consequent effect on the matter power-spectrum. By examining the correction it adds to power-spectrum of the underlying matter of large-scale-structures in the universe, we propose a unique avenue for indirectly detecting and constraining GWs. We begin by demonstrating this effect in the matter-dominated era, and then extend our analysis to encompass all epochs of cosmic evolution, utilizing standard perturbation theory to study the intricate interplay between GWs and matter perturbations. In addition, we delve into the fascinating realm of GWs modulation induced by scalar inhomogeneities. As GWs traverse the inhomogeneous regions of the universe, they undergo modulation due to the presence of scalar perturbations. This modulation effect, as we show, provides a unique signature for primordial chiral GWs, that can differentiate it from scalar-induced GWs. By studying the characteristics of modulated GWs, we gain valuable insights into the intricate dynamics of the early universe and the interaction between GWs and scalar perturbations.