Nesta tese estudamos os efeitos da desordem espacial e temporal na transição de fase entre a sobrevivência e extinção de populações biológicas. Na primeira parte estudamos um modelo epidemiológico com quatro estados. Apesar deste modelo não conter desordem, concluímos que seu comportamento crítico é o mesmo do processo de contato com desordem (espacial) quenched. Na segunda parte estudamos o movimento Browniano fracionário refletido, onde vimos que a combinação dos efeitos do ruído com correlações de longo alcance e a parede refletora cria uma singularidade em lei de potência na densidade de probabilidade da posição do caminhante. Por fim, estudamos a equação logística com desordem temporal através do mapeamento no movimento Browniano fracionário refletido. Neste último estudo vimos como as correlações de longo alcance mudam o comportamento crítico deste sistema. / We have studied the effects of spatial and temporal disorder at the phase transition between survival and extinction of biological populations. In the first part we studied a four states biological population model. Despite having no disorder, we have seen that its critical behavior is the same of the contact process with (spatial) quenched disorder. In the second part, we studied the reflected fractional Brownian motion, where the interplay between the correlated noise and the reflecting wall results in a power-law singularity in the probability density of the position of the walker. Finally, we deduced the critical properties of the logistic equation with temporal disorder by mapping it onto the reflected fractional Brownian motion. This mapping allow us to understand how long-range correlations change the critical behavior of this system.

Towards the end of the 1960s in France we witness the awakening of the memory of the Holocaust and the Occupation which coincides with the publication of Patrick Modiano’s first novel, La place de l’étoile. It is from this time that Jewish memory of the Holocaust begins to surface and we see the emergence of a literature of the post-Holocaust generation. Modiano belongs to this generation that, being deprived of a personal memory of the Holocaust, turns to this period in a quest for roots and identity. Like his Jewish colleagues, Modiano struggles to come to terms with a past that he has not experienced and an absence of memory. This dissertation analyses Modiano’s use of the period of the Holocaust as signifier of Jewish identity in four of his novels in order to highlight the role of the issue of Jewish identity in the construction of a textual identity / Vers la fin des années 60 on voit en France le réveil de la mémoire de la Shoah et de l’Occupation qui coïncide avec la publication du premier roman de Patrick Modiano, La place de l’étoile. C’est à partir de cette époque que la mémoire juive de la Shoah va pouvoir se faire entendre et qu’on constate l’émergence d’une littérature de la génération d’après la Shoah. Modiano appartient à cette génération qui, étant dépourvue d’une mémoire personnelle de la Shoah, se tourne vers cette période dans une quête de racines et d’identité. Comme ses confrères juifs, Modiano a du mal à se réconcilier avec un passé qu’il n’a pas vécu et une absence de mémoire. Cette étude examine de près le recours de Modiano aux années de la Shoah en tant que signifiant de l’identité juive dans quatre ouvrages afin de mettre en exergue le rôle de la problématique de l’identité juive dans la construction d’une identité textuelle chez cet écrivain / Linguistics and Modern Languages / M. A. (French)