Made available in DSpace on 2014-12-17T15:15:00Z (GMT). No. of bitstreams: 1 CalistratoSCN.pdf: 479133 bytes, checksum: 26f581ebc6e3cf1ced0922a5e989272c (MD5) Previous issue date: 2001-11-07 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / The present work investigates some consequences that arise from the use of a modifed lagrangean for the eletromagnetic feld in two diferent contexts: a spatially homogeneous and isotropic universe whose dynamics is driven by a magnetic feld plus a cosmological parameter A, and the problem of a static and charged point mass (charged black hole). In the cosmological case, three diferent general solutions were derived. The first, with a null cosmological parameter A, generalizes a particular solution obtained by Novello et al [gr-qc/9806076]. The second one admits a constant A and the third one allows A to be a time-dependent parameter that sustains a constant magnetic feld. The first two solutions are non-singular and exhibit in ationary periods. The third case studied shows an in ationary dynamics except for a short period of time. As for the problem of a charged point mass, the solutions of the Einstein-Maxwell equations are obtained and compared with the standard Reissner-Nordstrom solution. Contrary to what happens in the cosmological case, the physical singularity is not removed / No presente trabalho s?o investigadas algumas conseq??ncias da utiliza??o de uma nova lagrangeana para a eletrodin?mica em dois contextos: um universo espacialmente homog?neo e isotr?pico com campo magn?tico mais um par?metro cosmol?gico A e o problema da massa puntual caregada e est?tica (buraco negro carregado). No caso cosmol?gico, foram obtidas tr?s solu??es gerais: a primeira delas, para A=0, generaliza uma solu??o particular obrida por Novello et al [gr-qc/9806076]; a segunda admite um par?metro cosmol?gico constante e n?o-nulo e a terceira corresponde a um campo magn?tico constante sustentado por um A dependente do tempo. As duas primeiras solu??es s?o n?o-singulares e possuem per?odos inflacion?rios. A terceira solu??o apresenta uma din?mica inflacion?ria exceto por um curto intervalo de tempo. No contexto do problema da massa puntual carregada, a solu??o das equa??es de Einstein-Maxwell ? obtida e comparada com a solu??o padr?o de Reissner-Nordstr?m. Ao contr?rio do caso cosmol?gico, a singularidade f?isica n?o ? removida