Este projeto de mestrado tem por objetivo dar uma prova elementar do seguinte teorema de Tits, conhecido como Teorema da Alternativa de Tits: Seja G um grupo linear finitamente gerado sobre um corpo. Então G é solúvel por finito ou G contém um grupo livre não cíclico. Este teorema, que foi provado por J. Tits em 1972 [4], foi considerado pelo matemático J.P. Serre como um dos mais importantes resultados de álgebra do século XX. Quando dizemos uma prova elementar, não queremos absolutamente te dizer uma prova simples. Seguiremos a prova simplificada de John D. Dixon / This masters project aims to give an elementary proof of the following theorem of Tits, known as the Alternative Tits Theorem: Let G be a finitely generated linear group over a field. Then either G is solvable by finite or G contains a noncyclic free subgroup. This theorem was proved by J. Tits in 1972 [4], was considered by the mathematician J.P. Serre, as one of the most important algebra results of the XX century. When we say an elementary proof, we absolutely not mean a simple proof. We will follow the simplified proof of John D. Dixon

Les formules de Thomae classiques (1869) permettent de relier au moyen d'une relation algébrique les points branches d'une courbe hyperelliptique avec les thêta constantes de sa jacobienne. Ces formules donnent notamment un moyen de calculer les thêta constantes d'une courbe hyperelliptique connaissant ses points de ramification ou bien, à l'inverse, de retrouver la courbe en connaissant le theta null point de sa jacobienne. Ceci fournit une réalisation effective du théorème de Torelli. Plus récemment, plusieurs auteurs dont Zemel et Farkas ont proposé une généralisation de ces formules pour des courbes cycliques totalement ramifiées sur la droite projective. Nous nous intéressons dans cette thèse à une généralisation de ces formules pour des courbes galoisiennes résolubles de degré n sur la droite projective. La construction de telles formules suit la stratégie décrite par Farkas et Zemel. Cependant, les points non totalement ramifiés ne décrivent pas des points de n-torsion de la Jacobienne de la courbe via l'application d'Abel-Jacobi. Pour remédier à cet obstacle, nous composons T par theta, où T agit comme une moyenne décrite par un sous-groupe du groupe de Galois de la courbe possédant certaines propriétés. Afin de décrire les zéros de translatés de cette application composée, nous écrivons un analogue du théorème de Riemann sur les zéros de theta. Enfin, nous exhibons un exemple d'une courbe définie par un revêtement de degré 2 suivi de deux revêtements de degré 3 dans laquelle on obtient des formules de Thomae généralisées. / The classical Thomae formulae (1869) provide algebraic relations between the branch points of an hyperelliptic curve and the theta constants of its Jacobian. These formula can be seen as a way to calculate these theta constants from the data of the ramification points of the hyperelliptic curve or in the other way around, to find the curve whose Jacobian is given by its theta null point. This can be seen as an effective version of Torelli's theorem. More recently, several authors including Zemel and Farkas have proposed a generalization of these formula for cyclic curves that are totally ramified on the projective line. In this thesis, we are interested in a generalization of these formula for curves of degree n with a solvable Galois group over the projective line. The construction of such formula follows the strategy developed by Farkas and Zemel. However, the points that are not totally ramified don't describe n-torsion points on the Jacobian of the curve via the Abel-Jacobi map. In order to solve this difficulty, we consider the composed map of T by theta, where T is a mean described by a sub-group of the Galois group of the curve with several properties. We write an analogous of the Riemann's theorem in order to describe the zeros of translates of this composed map. Finally, we show an example of a curve defined by a cover of degree 2 followed by two covers of degree 3 for which we can compute generalized Thomae formulae.

Transformers have emerged as a powerful architecture for various tasks in natural language processing, computer vision, and multi-modal domains. Despite their success, understanding the computational capabilities and limitations of transformers remains a challenge. This work focuses on relating transformers to deterministic finite automata (DFAs) and empirically investigates the architecture's ability to simulate DFAs of varying complexities. We empirically explore the simulation of DFAs by transformers, specifically focusing on the solvable A4-DFA and the non-solvable A5-DFA. We conduct experiments to evaluate the in-distribution and out-of-distribution accuracy of sub-linear depth transformers with positive results on both accounts. Additionally, we examine the impact of widening the transformer to find even shallower transformers for the  A4-DFA. While no significant improvements are observed compared to the sub-linear depth transformers, further exploration of hyperparameters is needed for more reliable results.

京都大学 / 新制・課程博士 / 博士(理学) / 甲第24395号 / 理博第4894号 / 新制||理||1699(附属図書館) / 京都大学大学院理学研究科数学・数理解析専攻 / (主査)教授 玉川 安騎男, 教授 並河 良典, 教授 望月 新一 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

京都大学 / 新制・課程博士 / 博士(理学) / 甲第24398号 / 理博第4897号 / 新制||理||1700(附属図書館) / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)教授 佐藤 昌利, 教授 佐々 真一, 准教授 戸塚 圭介 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

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An exact quantum Monte Carlo algorithm for interacting particles in the spatial continuum is extended to exploit the massive parallelism offered by graphics processing units. Its efficacy is tested on the Calogero-Sutherland model describing a system of bosons interacting in one spatial dimension via an inverse square law. Due to the long range nature of the interactions, this model has proved difficult to simulate via conventional path integral Monte Carlo methods running on conventional processors. Using Graphics Processing Units, optimal speedup factors of up to 640 times are obtained for N = 126 particles. The known results for the ground state energy are confirmed and, for the first time, the effects of thermal fluctuations at finite temperature are explored.

The conjugacy length function of a group Γ determines, for a given a pair of conjugate elements u,v ∈ Γ, an upper bound for the shortest γ in Γ such that uγ = γv, relative to the lengths of u and v. This thesis focuses on estimating the conjugacy length function in certain finitely generated groups. We first look at a collection of solvable groups. We see how the lamplighter groups have a linear conjugacy length function; we find a cubic upper bound for free solvable groups; for solvable Baumslag--Solitar groups it is linear, while for a larger family of abelian-by-cyclic groups we get either a linear or exponential upper bound; also we show that for certain polycyclic metabelian groups it is at most exponential. We also investigate how taking a wreath product effects conjugacy length, as well as other group extensions. The Magnus embedding is an important tool in the study of free solvable groups. It embeds a free solvable group into a wreath product of a free abelian group and a free solvable group of shorter derived length. Within this thesis we show that the Magnus embedding is a quasi-isometric embedding. This result is not only used for obtaining an upper bound on the conjugacy length function of free solvable groups, but also for giving a lower bound for their L_p compression exponents. Conjugacy length is also studied between certain types of elements in lattices of higher-rank semisimple real Lie groups. In particular we obtain linear upper bounds for the length of a conjugator from the ambient Lie group within certain families of real hyperbolic elements and unipotent elements. For the former we use the geometry of the associated symmetric space, while for the latter algebraic techniques are employed.