Made available in DSpace on 2014-06-11T19:25:28Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-07-14Bitstream added on 2014-06-13T18:53:32Z : No. of bitstreams: 1 matulovic_m_me_mar.pdf: 351553 bytes, checksum: ce05b2472eda1483cbde0d4d3caf708d (MD5) / Dentre as diversas lógicas não-clássicas, que complementam o cálculo de predicados de primeira ordem, destacamos as lógicas moduladas. As lógicas moduladas são caracterizadas pela inclusão de um novo quantificador, chamado modulado, que tem a incumbência de interpretar aspectos indutivos de quantificadores das linguagens naturais. Como um caso particular de lógica modulada, a lógica do muito formaliza a noção intuitiva de “muitos”. O quantificador do muito é representado por G. Assim, uma sentença do tipo Gxα(x) deve ser entendida como “muitos indivíduos satisfazem a propriedade α”. Semanticamente, a noção de muitos está associada a uma estrutura matemática denominada família fechada superiormente e própria. Seja E um conjunto não vazio. Uma família própria fechada superiormente F em E é tal que: (i) F ⊆ P(E); (ii) E ∈ F; (iii) ∅ ∉ F; (iv) A ∈ F e A ⊆ B ⇒ B ∈ F. Intuitivamente, F caracteriza os conjuntos que possuem ‘muitos’ elementos. E, assim, o universo E possui muitos elementos; o ∅ não possui muitos elementos; e se A possui muitos elementos, então todo conjunto que contém A também possui muitos elementos. Com elementos sintáticos que caracterizam linguisticamente estas propriedades de F, pode-se verificar que a lógica do muito é correta e completa para uma estrutura de primeira ordem estendida por uma família própria fechada superiormente. A lógica do muito foi originalmente introduzida em um sistema dedutivo hilbertiano, baseado apenas em axiomas e regras de dedução. Neste trabalho, desenvolvemos um outro sistema dedutivo para a lógica do muito, porém num sistema de tablôs. Demonstramos, naturalmente, que esse novo sistema é equivalente ao sistema axiomático original. / Among the several non classical logics that complement the classical first-order logic, we detach the Modulated Logics. This class of logics is characterized by extending the classical logic by the introduction of a new generalized quantifier, called modulated quantifier, that has the attribution of interpreting some inductive aspects of quantifiers in any natural language. As a particular case of Modulated Logic, the Logic of Many formalize the intuitive notion of “many”. The quantifier of many is represented by G. Thus, a sentence of the type Gxα(x) must be understood like “many individuals satisfy the property α”. Semantically, the notion of many is associated with a mathematical structure named proper superiorly closed family. Let E be a non empty set. A proper superiorly closed family F in E is such that: (i) F ⊆ P(E); (ii) E ∈ F; (iii) ∅ ∉ F; (iv) A ∈ F e A ⊆ B ⇒ B ∈ F. Intuitively, F characterizes the sets which have “many” elements. The empty set ∅ does not have many elements. And if A has many elements, then any set which contains A, also has many elements. The logic of many has syntactical elements that caracterize linguisticaly these properties of F. We can verify that the Logic of Many is correct and complete for a first order structure extended by a proper superiorly closed family. The Logic of Many was originally introduced in a Hilbertian deductive system, based only on axioms and rules. In this work, we developed another deductive system for the Logic of Many, but in a tableaux system. We proof that this new system is equivalent to the original one.

Made available in DSpace on 2014-06-11T19:32:10Z (GMT). No. of bitstreams: 0 Previous issue date: 2012-04-04Bitstream added on 2014-06-13T18:43:09Z : No. of bitstreams: 1 seewald_ncc_dr_ift.pdf: 980110 bytes, checksum: a8da01736f6d240fb7a6880d23b95d14 (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / O objetivo da Tese é investigar a aplicabilidade e propor extensões do método do hamiltoniano termodinamicamente equivalente (MHTE) para sistemas de muitos corpos descritos por uma teoria de campos. Historicamente, o MHTE tem sua origem na teoria quântica de muitos corpos para descrever o fenômeno da supercondutividade. O método consiste na observação de que o hamiltoniano de um sistema pode ser diagonalizado exatamente através de uma transformação unitária quando um número finito de momentos transferidos que contribuem para a interação é levado em conta no limite termodinâmico. Essa transformação unitária depende explicitamente de funções de gap que podem ser determinadas através do método variacional de Gibbs. Na presente Tese, extensões do método são feitas visando aplicações em sistemas de muitos corpos em diferentes situações, tais como: transições de fase estáaticas, evolução temporal de parâmetros de ordem descrita por equações dinâmicas estocásticas do tipo Ginzburg-Landau-Langevin (GLL), teorias quânticas de campos escalares relativísticos e teorias de muitos corpos para sistemas fermiônicos não relativísticos. Mostra-se, em particular, que o MHTE é um esquema de aproximação sistemático e controlável que permite incorporar acoplamentos de componentes de Fourier de parâmetros de ordem além do modo zero, da mesma forma que em teorias quânticas relativísticas ou não relativísticas ele incorpora correlações não perturbativas entre as partículas além daquelas levadas em conta pelas tradicionais aproximações de campo médio. Métodos são desenvolvidos para obtermos soluções numéricas explícitas com o objetivo de avaliar a aplicabilidade do MHTE em alguns casos específicos. Particular atenção é dedicada ao controle de divergências de Rayleigh-Jeans nas simulações numéricas de equações de GLL / The general objective of the Thesis is to apply the Method of the Thermodynamically Equivalent Hamiltonian (MTEH) to many-body systems described by a field theory. Historically, the MTEH has its origins in the quantum theory of manybody systems to describe the phenomenon of superconductivity. The method is based on the observation that the Hamiltonian of the system can be diagonalized exactly with a unitary transformation when a finite number of transfer momenta of the interaction are taken into account in the thermodynamic limit. This unitary transformation depends explicitly on gap functions that can be determined with the use of the Gibbs variational principle. In the present Thesis, extensions of the method are made envisaging applications in many-body systems in different situations, like: static phase transitions, time evolution of order parameters described by dynamic stochastic Ginzburg-Landau-Langevin equations, relativistic quantum scalar field theories, and many-body theories for nonrelativistic fermionic systems. It is shown that the MTEH is a systematic and controllable approximation scheme that in the theory of phase transitions allows to incorporate Fourier modes of the order parameter beyond the zero mode, in the same way that in the relativistic and nonrelativistic theories it incorporates particle nonperturbative correlations beyond those taken into account by the traditional mean field approximation. Methods are developed to obtain explicit numerical solutions with the aim to assess the applicability of the MTEH in specific situations. Particular attention is devoted to the control of Rayleigh-Jeans ultraviolet divergences in the numerical simulations of Ginzburg-Landau-Langevin equations

Orientador: Gastão Inácio Krein / Banca: Marcus Benghi Pinto / Banca: Ney Lemke / Banca: Sandra dos Santos Padula / Banca: Yogiro Hama / Resumo: O objetivo da Tese é investigar a aplicabilidade e propor extensões do método do hamiltoniano termodinamicamente equivalente (MHTE) para sistemas de muitos corpos descritos por uma teoria de campos. Historicamente, o MHTE tem sua origem na teoria quântica de muitos corpos para descrever o fenômeno da supercondutividade. O método consiste na observação de que o hamiltoniano de um sistema pode ser diagonalizado exatamente através de uma transformação unitária quando um número finito de momentos transferidos que contribuem para a interação é levado em conta no limite termodinâmico. Essa transformação unitária depende explicitamente de funções de gap que podem ser determinadas através do método variacional de Gibbs. Na presente Tese, extensões do método são feitas visando aplicações em sistemas de muitos corpos em diferentes situações, tais como: transições de fase estáaticas, evolução temporal de parâmetros de ordem descrita por equações dinâmicas estocásticas do tipo Ginzburg-Landau-Langevin (GLL), teorias quânticas de campos escalares relativísticos e teorias de muitos corpos para sistemas fermiônicos não relativísticos. Mostra-se, em particular, que o MHTE é um esquema de aproximação sistemático e controlável que permite incorporar acoplamentos de componentes de Fourier de parâmetros de ordem além do modo zero, da mesma forma que em teorias quânticas relativísticas ou não relativísticas ele incorpora correlações não perturbativas entre as partículas além daquelas levadas em conta pelas tradicionais aproximações de campo médio. Métodos são desenvolvidos para obtermos soluções numéricas explícitas com o objetivo de avaliar a aplicabilidade do MHTE em alguns casos específicos. Particular atenção é dedicada ao controle de divergências de Rayleigh-Jeans nas simulações numéricas de equações de GLL / Abstract: The general objective of the Thesis is to apply the Method of the Thermodynamically Equivalent Hamiltonian (MTEH) to many-body systems described by a field theory. Historically, the MTEH has its origins in the quantum theory of manybody systems to describe the phenomenon of superconductivity. The method is based on the observation that the Hamiltonian of the system can be diagonalized exactly with a unitary transformation when a finite number of transfer momenta of the interaction are taken into account in the thermodynamic limit. This unitary transformation depends explicitly on gap functions that can be determined with the use of the Gibbs variational principle. In the present Thesis, extensions of the method are made envisaging applications in many-body systems in different situations, like: static phase transitions, time evolution of order parameters described by dynamic stochastic Ginzburg-Landau-Langevin equations, relativistic quantum scalar field theories, and many-body theories for nonrelativistic fermionic systems. It is shown that the MTEH is a systematic and controllable approximation scheme that in the theory of phase transitions allows to incorporate Fourier modes of the order parameter beyond the zero mode, in the same way that in the relativistic and nonrelativistic theories it incorporates particle nonperturbative correlations beyond those taken into account by the traditional mean field approximation. Methods are developed to obtain explicit numerical solutions with the aim to assess the applicability of the MTEH in specific situations. Particular attention is devoted to the control of Rayleigh-Jeans ultraviolet divergences in the numerical simulations of Ginzburg-Landau-Langevin equations / Doutor

O presente trabalho apresenta o estudo das propriedades da condensação de Bose-Einstein e da superfluidez em um sistema bosônico disposto em um arranjo unidimensional de potenciais periódicos em formato de anel. O Hamiltoniano efetivo usual em termos dos operadores de campo é implementado na representação construída em termos das funções de Bloch da primeira banda e o problema é resolvido por meio da sua diagonalização através de métodos numéricos. No limite de hopping pequeno, este modelo é essencialmente equivalente à representação usual do modelo de Bose-Hubbard, mas incorpora efeitos adicionais através das energias de Bloch de partícula independente e dos elementos da matriz de dois corpos na situação em que o hopping é grande [19]. Através da inclusão de rotação no sistema, as energias de partícula independente são forçadas a depender da velocidade angular. Isto implica, correspondentemente, uma dependência da velocidade angular nas funções de onda de partícula independente e nos resultados de muitos corpos obtidos através da diagonalização do Hamiltoniano. Com o objetivo de estudar a superfluidez, o critério de dois fluidos é empregado e através de resultados numéricos obtêm-se a variação da fração de superfluido com o quadrado da velocidade angular. Ainda, considera-se aqui uma expressão perturbativa para o parâmetro inercial do sistema expresso em termos das excitações do sistema sem rotação, o que permite relacionar as energias do sistema com rotação com aquelas do sistema sem rotação. Isto é particularmente interessante para obter a fração de superfluido em termos da informação espectral do sistema sem rotação. Resultados semelhantes podem ser encontrados através da definição de superfluido baseada na resposta do sistema a uma variação de fase, imposta através de condições de contorno torcidas [30, 33], mas com a diferença de que os desenvolvimentos aqui não fazem uso da hipótese do modo condensado. De maneira geral, os resultados numéricos obtidos indicam, que pelo menos para este sistema, as frações de superfluido e condensado são quantidades sem relação direta, sugerindo então que mesmo para sistemas gasosos diluídos a idéia de que a superfluidez é uma consequência da condensação de Bose-Einstein deve ser considerada com mais cuidado. / In this work we study the properties of Bose-Einstein condensation and superfluidity in a finite bosonic system in a 1-dimensional ring with a periodic potential under rotation. The usual field effective Hamiltonian is implemented in a representation constructed in terms of the first band Bloch functions and the problem is solved by numeric diagonalization. In the limit of small hopping, this model is essentially equivalent to the quasi-momentum representation of the usual Bose-Hubbard model but incorporates additional effects via Bloch single particle energies and two-body matrix elements in the case of large hopping [19]. By including rotation in the system we force the single particle energies to be a function of the angular velocity. This implies a corresponding angular velocity dependence of the single particle wavefunctions and many-body diagonalization results. In order to study superfluidity, we consider the two fluid criterion. Numerical results for the superfluid fraction involving the change of in rinsic ground state energy with the square of the angular velocity are obtained. We also consider a perturbative expression for the system inertial parameter expressed in terms of the excitation spectrum of the non rotating system, which enables us to relate the energies in the rotating system to the ones in the system without rotation. This is particularly interesting for obtaining superfluid fraction in terms of spectral information of the non rotating system. Similar results can be found by using the definition of superfluid fraction based on the response of the system to a phase variation imposed by means of twisted boundary conditions [30, 33], but with the difference that our developments do not assume the hypothesis of a condensate mode. Our numerical results indicate that in this system condensate and superfluid fractions are quite unrelated in terms of parameter values, indicating that even for dilute gases the concept that superfluidity is a consequence of Bose-Einstein condensation should be considered more carefully.

The ability to isolate single atomic layers of van der Waals materials has led to renewed interest in the electronic and optical properties of these materials as they can be fundamentally different at the monolayer limit. Moreover, these 2D crystals can be assembled together layer by layer, with controllable sequence and orientation, to form artificial materials that exhibit new features that are not found in monolayers nor bulk. Twisted bilayer graphene is one such prototype system formed by two monolayer graphene layers placed on top of each other with a twist angle between their lattices, whose electronic band structure depends on the twist angle. This thesis presents the efforts to explore the electronic and optical properties of twisted bilayer graphene by Raman spectroscopy and scanning tunneling microscopy measurements. We first synthesize twisted bilayer graphene with various twist angles via chemical vapor deposition. Using a combination of scanning tunneling microscopy and Raman spectroscopy, the twist angles are determined. The strength of the Raman G peak is sensitive to the electronic band structure of twisted bilayer graphene and therefore we use this peak to monitor changes upon doping. Our results demonstrate the ability to modify the electronic and optical properties of twisted bilayer graphene with doping. We also fabricate twisted bilayer graphene by controllable stacking of two graphene monolayers with a dry transfer technique. For twist angles smaller than one degree, many body interactions play an important role. It requires eight electrons per moire unit cell to fill up each band instead of four electrons in the case of a larger twist angle. For twist angles smaller than 0.4 degree, a network of domain walls separating AB and BA stacking regions forms, which are predicted to host topologically protected helical states. Using scanning tunneling microscopy and spectroscopy, these states are confirmed to appear on the domain walls when inversion symmetry is broken with an external electric field. We observe a double-line profile of these states on the domain walls, only occurring when the AB and BA regions are gaped. These states give rise to channels that could transport charge in a dissipationless manner making twisted bilayer graphene a promising platform to realize controllable topological networks for future applications.

This thesis is part of the European MANY project. The goal of MANY is to provide developers with tools to develop software for multi and many-core hardware platforms. This is the first thesis that is part of MANY at Enea. The thesis aims to provide a knowledge base about software on many-core at the Enea student research group. More than just providing a knowledge base, a part of the thesis is also to port Enea's operating system OSE to Tilera's many-core processor TILEpro64. The thesis shall also investigate the memory hierarchy and interconnection network of the Tilera processor. The knowledge base about software on many-core was constrained to investigating the shared memory model and operating systems for many-core. This was achieved by investigating prominent academic research about operating systems for many-core processors. The conclusion was that a shared memory model does not scale and for the operating system case, operating systems shall be designed with scalability as one of the most important requirements. This thesis has implemented the hardware abstraction layer required to execute a single-core version of OSE on the TILEpro architecture. This was done in three steps. The Tilera hardware and the OSE software platform were investigated. After that, an OSE target port was chosen as reference architecture. Finally, the hardware dependent parts of the reference software were modified. A foundation has been made for future development.

With the advent of mass-market consumer multicore processors, the growing trend in the consumer off-the-shelf general purpose processor industry has moved away from increasing clock frequency as the classical approach for achieving higher performance. This is commonly attributed to the well-known problems of power consumption and heat dissipation with high frequencies and voltage. This paradigm shift has prompted research into a relatively new field of "many-core" processors, such as the Intel Single-chip Cloud Computer. The SCC is a concept vehicle, an experimental homogenous architecture employing 48 IA32 cores interconnected by a high-speed communication network. As similar multiprocessor systems, such as the Cell Broadband Engine, demonstrate a significantly higher aggregate bandwidth in the interconnect network than in memory, we examine the viability of a pipelined approach to sorting on the Intel SCC. By tailoring an algorithm to the architecture, we investigate whether this is also the case with the SCC and whether employing a pipelining technique alleviates the classical memory bottleneck problem or provides any performance benefits. For this purpose, we employ and combine different classic algorithms, most significantly, parallel mergesort and samplesort.

Ce travail a été effectué dans le contexte d'un projet financé par l'ERC, Defying Amdahl's Law (DAL), dont l'objectif est d'explorer les techniques micro-architecturales améliorant la performance des processeurs multi-cœurs futurs. Le projet prévoit que malgré les efforts investis dans le développement de programmes parallèles, la majorité des codes auront toujours une quantité signifiante de code séquentiel. Pour cette raison, il est primordial de continuer à améliorer la performance des sections séquentielles des-dits programmes. Le travail de recherche de cette thèse porte principalement sur l'étude des différences entre les sections parallèles et les sections séquentielles de programmes multithreadés (MT) existants. L'exploration de l'espace de conception des futurs processeurs multi-cœurs est aussi traitée, tout en gardant à l'esprit les exigences concernant ces deux types de sections ainsi que le compromis performance-surface. / This thesis work is done in the general context of the ERC, funded Defying Amdahl's Law (DAL) project which aims at exploring the micro-architectural techniques that will enable high performance on future many-core processors. The project envisions that despite future huge investments in the development of parallel applications and porting it to the parallel architectures, most applications will still exhibit a significant amount of sequential code sections and, hence, we should still focus on improving the performance of the serial sections of the application. In this thesis, the research work primarily focuses on studying the difference between parallel and serial sections of the existing multi-threaded (MT) programs and exploring the design space with respect to the processor core requirement for the serial and parallel sections in future many-core with area-performance tradeoff as a primary goal.

Automotive systems have transitioned from basic transportation utilities to sophisticated systems. The rapid increase in functionality comes along with a steep increase in software complexity. This manifests itself in a surge of the number of functionalities as well as the complexity of existing functions. To cope with this transition, current trends shift away from today’s distributed architectures towards integrated architectures, where previously distributed functionality is consolidated on fewer, more powerful, computers. This can ease the integration process, reduce the hardware complexity, and ultimately save costs. One promising hardware platform for these powerful embedded computers is the many-core processor. A many-core processor hosts a vast number of compute cores, that are partitioned on tiles which are connected by a Network-on-Chip. These natural partitions can provide exclusive execution spaces for different applications, since most resources are not shared among them. Hence, natural building blocks towards temporally and spatially separated execution spaces exist as a result of the hardware architecture. Additionally to the traditional task local deadlines, automotive applications are often subject to timing constraints on the data propagation through a chain of semantically related tasks. Such requirements pose challenges to the system designer as they are only able to verify them after the system synthesis (i.e. very late in the design process). In this thesis, we present methods that transform complex timing constraints on the data propagation delay to precedence constraints between individual jobs. An execution framework for the cluster of the many-core is proposed that allows access to cluster external memory while it avoids contention on shared resources by design. A partitioning and configuration of the Network-on-Chip provides isolation between the different applications and reduces the access time from the clusters to external memory. Moreover, methods that facilitate the verification of data propagation delays in each development step are provided.

In a many-body fermionic system, the suppression of continuous transitions to absolute zero can result in a low temperature quantum fluid which deviates strongly from typical metallic behaviour; unconventional superconductivity can be induced by the strange metal region surrounding the zero-temperature phase transition. In this thesis we focus on three systems which demonstrate a highly tunable phase transition, with the aim of pushing them toward the border of a zero-temperature phase transition, and potentially superconductivity. CeAgSb2 is a uniaxial 4f ferromagnet, where physical pressure or a transverse field may be used to tune the magnetic transition towards T = 0 K. Our investigations, however, did not reveal the presence of superconductivity. It is likely that the field tuned transition does not correspond to a true critical point, whilst the high pressure region may be occupied by an antiferromagnetic phase, with the true critical point at higher pressures. However, other interesting features emerge in the electrical resistivity and AC-susceptibility, along with novel thermodynamic signatures linking the magnetisation to the specific heat. The doping series Lu(1-x)YxFe2Ge2 shows an antiferromagnetic transition which is suppressed to absolute zero at a critical concentration x_c=0.2. YFe2Ge2 displays anomalous low temperature behaviour consistent with the proximity to quantum critical fluctuations, along with a superconducting transition which appears in the electrical resistivity beneath a critical temperature of T_c ~ 1.7 K. Using low temperature DC magnetisation measurements, we show that this is a bulk effect, and that the superconductivity in YFe2Ge2 is of type-II. The thermodynamic and BCS properties of the superconducting phase are analysed in line with the parameters we extract experimentally. The superconducting 3-4-13 stannides (Ca,Sr)3Ir4Sn13 show a high temperature structural transition which may be suppressed by the application of hydrostatic pressure or effective chemical pressure. A superconducting dome is found, which appears to peak near where the structural transition extrapolates to zero temperature. Anomalous exponents are seen in the electrical resistivity over a wide temperature range. We investigate the influence of pressure on the superconducting critical temperature in Ca3Ir4Sn13 and the related compound Co3Ca4Sn13, along with an analysis of the upper critical field and flux-line phenomena in Ca3Ir4Sn13 and Sr3Ir4Sn13.