Medeiros, José Renan deSouza, Rhimon Alves de Assis2025-06-162025-06-162025-02-27SOUZA, Rhimon Alves de Assis. Comportamento multifractal e variabilidade em AGNs: estudo de quasares amplificados por lente gravitacional e análise espectral multibanda. Orientador: Dr. José Renan de Medeiros. 2025. 110f. Tese (Doutorado em Física) - Centro de Ciências Exatas e da Terra, Universidade Federal do Rio Grande do Norte, Natal, 2025.https://repositorio.ufrn.br/handle/123456789/63964The study of quasars with images distorted by gravitational lensing provides a unique opportunity to test astrophysical theories, such as the nature of dark matter and the cosmological model. The analysis of the light curves of these quasars is essential, as it yields critical information about the properties of the lensing object and the emitting regions. The aim of this research is to investigate multifractal behavior in lensed quasars, examining its relationship with the surrounding environment and the impact of microlensing on variability. In this work, we demonstrate the connection between multifractality and variability in images A and B (formed by gravitational lensing) of 14 quasars, selected based on the availability of long-term, high-cadence time series observations. Furthermore, a multi-band analysis was implemented to study variability across different structures of the Active Galactic Nucleus (AGN), providing insights into the physical processes occurring in distinct regions of the object. To this end, the second part of this study focuses on the analysis of the AGN Mrk 421, aiming to examine the multifractality of light curves across various emission bands, correlate multifractal metrics with variability, and thus establish nonlinear statistical analysis tools as a robust framework for the study of variability in AGNs.pt-BRAcesso AbertoMultifractalidadeQuasaresLente gravitacionaldoctoralThesisCIENCIAS EXATAS E DA TERRA::FISICA