Teoria de perturbações lineares num modelo intrinsecamente simétrico

Abstract

Contemporary cosmology is largely grounded in the standard ΛCDM model, based on the Friedmann–Lemaître–Robertson–Walker (FLRW) metric and on the Cosmological Principle, which assumes large-scale homogeneity and isotropy. This model has been highly successful in describing cosmic expansion, the anisotropies of the cosmic microwave background, and the formation of large-scale structures, although its formulation depends on the introduction of components that are not yet fully understood, such as dark matter and dark energy, in addition to assuming global symmetries that contrast with the observed inhomogeneities, such as clusters, filaments, and cosmic voids. In light of these limitations, alternative models have been developed that relax the conditions of the Cosmological Principle, such as the Lemaître–Tolman–Bondi (LTB), Szekeres, and Locally Rotationally Symmetric (LRS) models, allowing for more general matter distributions. More recently, intrinsically symmetric models have emerged, which preserve internal symmetries without requiring global homogeneity, providing a more flexible framework to investigate the effects of inhomogeneities on cosmological parameters. In this work, we develop the linear scalar perturbation framework for intrinsically symmetric models, analyzing how the presence of spatial gradients in the geometric background alters the evolution equations of the fluctuations. Our goal is to establish the theoretical basis to confront these models with the ΛCDM paradigm and investigate potential observational signatures of inhomogeneity.