京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第22823号 / 理博第4633号 / 新制||理||1666(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)准教授 矢野 孝次, 教授 泉 正己, 教授 日野 正訓 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

A Schur ring is a subring of the group algebra with a basis that is formed by a partition of the group. These subrings were initially used to study finite permutation groups, and classifications of Schur rings over various finite groups have been studied. Here we investigate Schur rings over various infinite groups, including free groups. We classify Schur rings over the infinite cyclic group.

Orientador: Marcelo Reicher Soares / Resumo: O objetivo desse trabalho é apresentar, de forma rigorosa, como a matemática aborda o conceito de infinito e propor uma sequência de atividades para que o professor possa explorar esse tema com seus alunos de forma inovadora e estimulante. Muito do que é compreendido acerca do infinito se deve às ideias desenvolvidas por Georg Cantor, que estabeleceu a teoria dos números cardinais transfinitos, gerando uma série de resultados surpreendentes, que serão apresentados ao longo dessa dissertação. Cantor descobriu que existem diversos tipos de infinito e definiu critérios para classificá-los e compará-los. Para compreender esta teoria, é fundamental recordar os conceitos básicos da teoria de conjuntos e funções. Além disso, serão apresentados formalmente os números naturais através dos axiomas de Peano, bem como suas operações e propriedades. A partir deste, será construído o conjunto dos números inteiros, racionais e reais. Dessa forma, será possível definir formalmente a noção de conjunto finito e infinito, bem como a noção de conjuntos enumeráveis, e não-enumeráveis, e estabelecer critérios para comparar a cardinalidade de tais conjuntos. O trabalho é finalizado com a apresentação de uma proposta didática voltada para os alunos de ensino médio, sustentado no relato de duas experiências de sua aplicação. O tema é abordado utilizando atividades diferenciadas e fundamentadas no cotidiano, visando com isto contribuir para que os alunos apresentem um maior interesse e uma participaçã... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The aim of this work is to present in a rigorous way how mathematics approaches the concept of the in nite and to propose a sequence of activities so that the teacher can explore this theme with his students in an innovative and stimulating way. Much of what is understood about infinite is due to the ideas developed by Georg Cantor who established the theory of transfinite cardinal numbers generating a series of surprising results that will be presented throughout this dissertation. Cantor found that there are several types of infinite and defined criteria for classifying and comparing them. To understand this theory it is essential to remember the basic concepts of set and function theory. In addition natural numbers will be formally presented through Peano axioms as well as their operations and properties. From the natural numbers the sets of integers, rationals and reals will be constructed. Then it will be possible to formally de ne the notions of finite and infinite sets as well as the notions of countable and uncountable sets and establish criteria for comparing the cardinality of such sets. The work is concluded with the presentation of a didactic proposal aimed at high school students supported by the report of two experiences of its application. The theme is presented through difierent activities, based on daily life, aiming to contribute to the students to show more interest and participate more actively in the classes. / Mestre

Nous reconsidérons les arguments de Zénon d’Élée dits de l’« Achille » et de la « Dichotomie », en réunissant les perspectives de plusieurs disciplines, dont l’histoire de la philosophie ancienne, l’histoire et la philosophie des mathématiques, et la philosophie du temps. Nous soutenons que les réponses ordinairement données à ces arguments au XXe siècle, d’après lesquelles la mathématique moderne nous donne les moyens de dissoudre l’aporie, sont erronées et s’accompagnent d’une vue faussée sur le problème originel, notamment sur le concept d’infini qu’il implique. Dans la première partie, nous étudions les sources sur Zénon et sur son contexte de réception, pour établir que l’infini est chez lui second par rapport à l’idée d’inachevabilité, qui découle d’un mode de raisonnement nouveau qu’on peut nommer « itératif indéfini ». Nous examinons comment Zénon a utilisé ce raisonnement dans l’élaboration d’apories dialectiques, et comment l’ensemble des systèmes antiques étaient susceptibles de résoudre ces dernières. Dans la seconde partie, nous défendons l’aporie zénonienne du mouvement. Nous montrons qu’elle repose sur un principe que nous nommons « principe d’achevabilité », lui-même ancré dans notre intuition temporelle du passage. À travers la considération de la littérature sur les « supertasks », des problèmes concernant la réalité et la nature du temps, des différents concepts d’infini, et de la réflexion métamathématique, nous montrons à la fois pourquoi les théories de l’infini mathématique sont, de fait, la seule raison conduisant à rejeter le principe d’achevabilité, et pourquoi elles ne sont pas, de droit, en mesure de justifier ce rejet. / We reconsider Zeno of Elea’s arguments known as “Achilles” and the “Dichotomy”, bringing together perspectives from several disciplines, including the history of ancient philosophy, the history and philosophy of mathematics and the philosophy of time. We contend that the usual contemporary answers to these arguments – according to which modern mathematics allow us to dissolve the aporia – are wrong, and carry a false view of the original problem, especially of the concept of infinity it implies. In the first part of the dissertation, we study the sources relevant to Zeno and his arguments’ reception context, in order to establish that Zeno’s infinite is dependant upon an idea of unachievability, acquired through to a new mode of reasoning that we call “indefinite iterative”. We examine the ways Zeno used this mode of reasoning in order to design dialectical aporias, and how ancient philosophical systems were capable of solving them. In the second part, we vindicate Zeno’s aporia of motion. We show that it rests on what we call “the achievability principle”, that itself is anchored in our intuition of passage. Through the consideration of problems relevant to so-called ‘supertasks’, to the reality and the nature of time, to the notion of infinity and to the metamathematical debate, we show, at the same time, how mathematical theories of the infinite are the only de facto reason to deny the achievability principle, and how they cannot, de jure, justify such a denial.

Rotational hydraulic actuators, e.g. motors, provide infinite stroke as there is no conceptual limit to how far they can turn. By contrast linear hydraulic actuators like cylinders provide only limited stroke by concept. In the world of electrical drives, linear motors provide infinite stroke also for linear motion. In hydraulics, the presented Hydraulic Infinite Linear Actuator is a novelty. This paper presents the novel Hydraulic Infinite Linear Actuator (HILA). The contribution is an assessment of properties relevant for control like high hydraulic stiffness and is based on analysis, simulation and measurements.

No description available.

Comics have been around for centuries and have had different culturalmeanings depending on era, genre and country. Toward the end of the 20thcentury and the start of the 21st century, we experienced the rise of theinternet as well as the normalization of home computers and with that,comics also started inhabiting the digital space. The digital space opens upfor opportunities of multimedia and new ways of interacting with comics, butmost comics maintain the formats of their printed counterparts.The goal of this thesis is to contribute knowledge to both interaction designpractice as well as digital comics. This is done by conducting research throughdesign and interaction-driven design and through them, launch anexploration into how different interactions affect the experience of reading.User tests as well as a workshop was conducted in order to help articulate theexperience. The conclusions reached were that a more active way ofinteracting (i.e. scrolling for instance) appeared to be preferable to othermore static ways of interacting. The usage of the digital space appeared to insome cases enhance the experience of reading but it was closely connected tothe nature of the interactions.

The Chow/Van der Waerden approach to algebraic cycles via resultants is elaborated and used to give a purely algebraic proof for the algebraicity of the complex suspension over arbitrary fields. The algebraicity of the join pairing on Chow varieties then follows over the complex numbers. The approach implies a more algebraic proof of Lawson´s complex suspension theorem in characteristic 0. The continuity of the action of the linear isometries operad on the group completion of the stable Chow variety is a consequence. Further Hoyt´s proof of the independence of the algebraic-continuous homeomorphism type of Chow varieties on embeddings is rectified and worked out over arbitrary fields.

This (Diplom-) thesis deals with the particle trajectories of an incompressible and ideal fluid flow in 𝑛 ≥ 2 dimensions. It presents a complete and detailed proof of the surprising fact that the trajectories of a smooth solution of the incompressible Euler equations are locally analytic in time. In following the approach of P. Serfati, a complex ordinary differential equation (ODE) is investigated which can be seen as a complex extension of a partial differential equation, which is solved by the trajectories. The right hand side of this ODE is in fact given by a singular integral operator which coincides with the pressure gradient along the trajectories. Eventually, we may apply the Cauchy-Lipschitz existence theorem involving holomorphic maps between complex Banach spaces in order to get a unique solution for the above mentioned ODE. This solution is real-analytic in time and coincides with the particle trajectories.

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第20882号 / 理博第4334号 / 新制||理||1623(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 加藤 毅, 教授 上 正明, 准教授 入谷 寛 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM