La description détaillée des systèmes désordonnés et vitreux représente un défi central en physique statistique et de la matière condensée, puisqu'à ce jour il n'existe pas de théorie unique et établie permettant de comprendre ces systèmes, pourtant omniprésents.Ce travail de recherche est lié en particulier à l'étude des matériaux vitreux à basse température. Plus précisément, si l'on considère des systèmes formés par un ensemble de particules athermiques avec des interactions répulsives de portée finie, en augmentant la densité, on peut observer une transition dite d'encombrement ("jamming"). Celle-ci consiste en un blocage des degrés de liberté accompagné par une augmentation spectaculaire de la rigidité du matériau.Nous étudierons ce problème à l’aide d’une analogie formelle entre des modèles de sphères et le perceptron, un modèle théorique qui développe une transition d'encombrement et des phénomènes de frustration typiques des systèmes désordonnés.En tant que modèle en champ moyen, il permet d'obtenir des résultats analytiques précis et généralisables à des systèmes à haute dimension.L'enjeu majeur de cette étude est de reconstruire le spectre des modes de vibration et toutes les propriétés pertinentes d'une phase spécifique (correspondant au régime dit des sphères dures).Dans ce cadre, nous dériverons le potentiel effectif en fonction des paramètres d'ordre du modèle et nous montrerons qu'il est dominé à proximité du point de jamming par une interaction logarithmique non triviale, qui clarifiera le lien entre les forces de contact et les distances moyennes entre les particules, dans la région critique et au-delà.Comprendre pleinement la transition d'encombrement et les propriétés du perceptron nous permettra de faire des progrès dans plusieurs domaines reliés. En premier lieu, cela peut conduire à une théorie complète des systèmes amorphes, à la fois en dimension infinie et en dimension finie.De plus, le modèle du perceptron semble avoir un lien étroit avec des problèmes dits de Von Neumann. En effet, les systèmes biologiques et écologiques développent souvent des propriétés liées à une condition pseudo-critique en mettant en oeuvre des mécanismes d'optimisation de ressource-consommation.Est-il possible d'identifier un régime caractérisé par une brisure de symétrie? Quel serait le spectre de fluctuations d'énergie dans ces systèmes?Ce ne sont que quelques-unes des questions auxquelles nous essayerons de répondre dans cette thèse.Cependant, l'approximation de champ moyen peut parfois fournir des informationsincorrectes ou trompeuses, en particulier dans l'étude de certaines transitions de phase et la détermination des dimensions critiques inférieure et supérieure.Afin d'avoir une vue d'ensemble et pouvoir manipuler correctement des systèmes en dimension finie, dans la suite de la thèse nous discuterons comment obtenir un développement perturbatif systématique, applicable à tout modèle, à condition que ce dernier soit défini sur un réseau ou un graphe biparti.Notre motivation est en particulier liée à la possibilité d'étudier certaines transitions de phase du second ordre qui existent sur le réseau de Bethe - c'est-à-dire un réseau en arbre sans boucles dont chaque noeud a une connectivité fixe - mais qui sont qualitativement différentes ou absentes dans le modèle entièrement connecté correspondant. / The detailed description of disordered and glassy systems represents an open problem in statistical physics and condensed matter. As yet, there is no single, well-established theory allowing to understand such systems. The research presented in this thesis is related in particular to the study of glassy materials in the low-temperature regime. More precisely, considering systems formed by athermal particles subject to repulsive short-range interactions, upon progressively increasing the density, a so-called jamming transition can be detected. It entails a freezing of the degrees of freedom and hence a huge increase of the material rigidity.We shall study this problem in view of a formal analogy between sphere models and the perceptron, a theoretical model undergoing a jamming transition and frustration phenomena typical of disordered systems. Being a mean-field model, it allows to obtain exact analytical results, which are generalizable to more complex high-dimensional settings.The main aim is to reconstruct the vibrational spectrum and all the relevant properties of a specific phase of the perceptron, corresponding to the hard-sphere regime.In this framework, we will derive the effective potential as a function of the gaps between and forces among the particles, and we will show that it is dominated by a non-trivial logarithmic interaction near the jamming point. This interaction in turn will clarify the relations existing between the relevant variables of the system, in the critical jamming region and beyond.Understanding the jamming transition and the perceptron properties will allow us to make progress in several related fields. First, this study could lay part of the groundwork towards a complete theory of amorphous systems, in both infinite and finite dimensions. Furthermore, the perceptron model seems to a have a close connection with the so-called Von Neumann problems. Indeed, biological and ecological systems often develop pseudo-critical properties and give rise to general mechanisms of resource-consumption optimisation.Is the identification of a broken symmetry regime possible? What would it yield in terms of the spectrum of the energy fluctuations?These are just a few questions we shall attempt to answer in this context.However, the mean-field approximation can sometimes provide wrong or misleading information, especially in studying certain phase transitions and determining the exact lower and upper critical dimensions. To have a broad perspective and correctly deal with finite-dimensional systems, in the second part of the thesis we will discuss obtaining a systematic perturbative expansion which can be applied to any model, as long as defined on a lattice or a bipartite graph.Our motivation is in particular due to the possibility of studying relevant second-order phase transitions which exist on the Bethe lattice — a lattice with a locally tree-like structure and fixed connectivity for each node — but which are qualitatively different or absent in the corresponding fully-connected version.

[pt] O presente trabalho de pesquisa concentra-se na área de estudos da linguagem, constando de dois troncos principais: um primeiro de análise teórica, em que se abordam questões de filosofia da linguagem e filosofia estética; e um outro de linguística aplicada, com a tradução comentada para o italiano de trechos do livro Ó (2008), de Nuno Ramos. Consta também um apêndice com a tradução integral do livro. Particularmente na primeira parte da tese serão abordadas questões relativas à análise e identificação dos procedimentos estéticos da escrita de Nuno Ramos, tentando entender suas relações com as práticas de artes plásticas e relativas contaminações, abordando a obra na perspectiva da literatura nos seus campos expandidos. Os procedimentos e técnicas usados na escrita e sua relação com as artes plásticas serão investigados de forma a entender a operação estética subjacente, investigando de que forma, a partir das características da obra, instaurar-se-ia uma relação de reciprocidade com o leitor ao qual caberia um papel ativo na produção de sentido. Os procedimentos estéticos usados pelo autor serão relacionados à sua poética de multi-artista, especialmente, na relação entre as palavras e as coisas, que se traduz no embate entre linguagem e matéria. A segunda parte, de linguística aplicada, envolve a prática tradutória stricto sensu a partir das análises desenvolvidas na seção anterior. Com base na leitura e análise da obra, e acrescentando uma parte teórico-metodológica específica sobre tradução, são definidas as linhas norteadoras das escolhas tradutórias, identificando técnicas, práticas e soluções de tradução que possam restituir no texto italiano a mesma operação estética do texto fonte. Particularmente importante será a realização, através de uma tradução que reescreva os procedimentos estéticos do texto português, conseguir recriar a relação de reciprocidade entre obra e o leitor, de forma a ativar o empasses de percepção, base para o desenvolvimento de espaços de pensamento ético-político. Uma vez identificadas as linhas tradutórias, elas serão desenvolvidas e exemplificadas através de trechos de tradução comentada. / [en] This research - in the area of language studies - consists of two main sections: the first of theoretical analysis, in which we deal with issues related to the philosophy of language and aesthetic; another of applied linguistics, in which will be presented the commented translation in Italian of selected extracts from the book Ó (2008) by Nuno Ramos. The complete translation of the book is presented as appendix to this thesis. In the first part will be investigated issues related to the analysis and identification of the aesthetic procedures of Nuno Ramos writing, also trying to understand their relationships with plastic arts practices and possible contaminations; the work will be also investigated from the perspective of literature and its extension in different expressive fields. The procedures and techniques used in writing and its relationship with the plastic arts will be examined in order to understand and identify what type of aesthetic operation underlies, analyzing how, starting from the salient features of the work, a relationship of reciprocity could be established between the work and the reader who would have an active role in the production of meaning. The aesthetic procedures implemented by the author will be related to his poetics as multiartist, especially in the relationship between words and things, which leads into a clash between language and matter. The second part, of applied linguistics, concerns the translation practice stricto sensu, realized starting from the analyzes developed in the previous section. Based on the reading and interpretation of the work - also implementing a specific theoreticalmethodological part on translation -, will be defined the guidelines for the translation choices, highlighting techniques, practices and translation solutions that can reproduce the same aesthetic operation of the source text in the Italian text . It will be particularly important to recreate, through a translation that rewrites the aesthetic procedures of the Portuguese text, a relationship of reciprocity between the work and the reader, in order to activate the same impasse of perception - a fundamental element to open spaces for an ethical-political thinking. Once the guidelines are defined, they will be developed and exemplified through extracts of commented translation. / [it] Il presente lavoro di ricerca - afferente all area di studi del linguaggio - si compone di due tronchi principali: il primo di analisi teorica, in ci si affrontando questioni relative alla filosofia del linguaggio e alla filosofia estetica; un altro di linguistica applicata, con la traduzione commentata in italiano di estratti selezionati del libro Ó (2008) di Nuno Ramos. La traduzione integrale del libro costituisce appendice alla presente tesi. Nella prima parte saranno affrontate questioni relative all analisi e identificazione dei procedimenti estetici della scrittura di Nuno Ramos, provando a comprenderne le relazioni con le pratiche delle arti plastiche e relative contaminazioni, investigando l opera sotto la prospettiva della letteratura e la sua estensione in campi espressivi diversi. I procedimenti e le tecniche usate nella scrittura e la sua relazione con le arti plastiche saranno investigati in modo da comprendere e identificare che tipo di operazione estetica vi soggiace, analizzando in che modo, proprio partendo dalle caratteristiche salienti dell opera, si instaurerebbe una relazione di reciprocità tra l opera e il lettore al quale toccherebbe il ruolo attivo nella produzione di senso. I procedimenti estetici messi in atto dall autore saranno relazionati alla sua poetica di multi-artista, soprattutto nel rapporto tra le parole e le cose, che si traduce in uno scontro tra linguaggio e materia.