Antonio Carlos Gomes (1836-1896) is considered one of the most important Brazilian composers and was the first New World composer whose work was accepted in Europe. His opera Fosca, though, was never discussed in depth and should be recognized as an important work in the history of the nineteenth century Italian opera for its skillful use of themes and motives. The Brazilian composer and musicologist Mario de Andrade presented a study of the principal themes in 1936, in commemoration of the centennial of Carlos Gomes' birth, but there is no record of a thorough study that shows the magnitude of Carlos Gomes' application of his motivic and thematic technique in this work.In this document, the author identifies the principal themes and motives, and demonstrates how the composer systematically used them to enhance the drama and lend coherence to the work as a whole. Gomes, in Fosca, used the technique to such extent that every major character in the opera has a minimum of one theme related to him or her. The leading role Fosca has many themes to represent her different feelings throughout the opera. There are also themes representing specific feelings between two people, and themes related to the chorus as well. Gomes uses his themes to contribute to the drama as active psychological elements and not simply as ornamentation.The recurring themes in Fosca are easily heard and recognized, but this does not mean that Gomes used them in a rudimentary or merely mechanical manner. Gomes' simplicity proves to be a useful tool in ensuring musical and dramatic continuity, offering us an idea of his broader goal as a musical dramatist.

In this thesis we push forward techniques to learn about the large scale structure formation of the universe. The approach is from theory, observations and simulations. From theory we study the growth of four non standard cosmological models: DGP model, Cardassian model, Chaplygin gas model and Coupled Quintessence model. From observations we look at the ISW effect by means of the cross-correlation between CMB maps and galaxy survey. From a compilation of data we contrain the cosmological parameters and give new evidence of dark energy. We also introduce a new method to compute errors in configuration space and compare it with other methods in the literature. This method takes into account the geometry of the suveys and it is shown to give accurate results at large angles. In this thesis we also use large dark matter simulations to study the clustering and the local halo bias model. KEY WORDS: large scale structure, structure formation, dark energy, halo bias / CATALÀ:En aquesta tesi estudiem la formació d'estructures a gran escala de l'univers apoximant-nos-hi des de la teoria, les observacions i les simulacions. Respecte la teoria estudiem el creixement d'estructures en quatre models no estàndards: el model DGP, el model Cardassian, el model de gas de Chaplygin i el model de Quintessècia acoplada. De les observacions estudiem la formació d'estructura a partir de correlacions entre mapes de galàxies amb mapes del CMB, les quals mesuren l'efecte ISW. A partir d'una compilació que d'aquestes mesures restringim els paràmetres cosmològics i mostrem nova evidència de l'energia fosca. També introduim un nou mètode per a calcular els errors de les correlacions en l'espai de configuració. Comparem aquest mètode amb d'altres i mostrem que estima bé els errors a angles grans, doncs tenim en compte l'area del cel observada. Finalment utilitzem simulacions de matéria fosca per estudiar el clustering i el model de bias local. / RESUMEN CASTELLANO:En esta tesis estudiamos la formación de estructura en el universo en las vertientes teórica, observacional y con simulaciones. Respeto a la teoria estudiamos el crecimiento de estructuras en cuatro modelos no estándares: el modelo DGP, el modelo Cardassian, el modelo de gas de Chaplygin y el modelo de Quintessencia acoplado. Respecto a las observaciones estudiamos la formación de estructura a partir de las correlaciones entre el CMB y mapas de galaxias, las cuales miden el efecto ISW. A partir de una compilación de estas medidas restringimos los parámetros cosmológicos dando nueva evidencia de la energía oscura. También introducimos un nuevo método para el cálculo de errores en espacio de configuración y mostramos, al compararlo con otros, que estima bien los errores a grandes ángulos puesto que tenemos en cuenta la geometria de área observada. Finalmente, utilizando simulaciones de materia oscura, estudiamos el clustering y el modelo de bias local. PALABRAS CLAVE: Estructura a gran escala, energia oscura, bias en halos, formación de estructura.