In the 1990s, physicists started looking beyond their disciplinary boundaries by using their methods to study various problems usually thrown up by financial economics. This dissertation deals with this extension of physics outside its disciplinary borders. It seeks to determine what sort of discipline econophysics is in relation to physics and to economics, how its emergence was made possible, and what sort of knowledge it produces. Using a variety of evidence including bibliometric analysis Chapter 1 explores the field’s disciplinary identity as a branch of physics even though its intellectual heart is better seen as the re-emergence of a 1960s research programme initiated in economics. Chapter 2 is historical: it identifies the key role played by the Santa Fe Institute and its pioneering complexity research in the shaping of methodological horizons of econophysics. These are in turn investigated in Chapter 3, which argues that there are in fact three methodological strands: statistical econophysics, bottom-up agent-based econophysics, and top-down agent-based econophysics. Viewed from a Lakatosian perspective they all share a conceptual hard-core but articulate the protective belt in distinctly different ways. The last and final chapter is devoted to the way econophysicists produce and justify their knowledge. It shows that econophysics operates by proposing empirically adequate analogies between physical and other systems in exactly the ways emphasised by Pierre Duhem. The contrast between such use of analogy in econophysics and modeling practices implemented by financial economics explains why econophysics remains so controversial to economists.

This thesis examines various reductive case studies in thermal physics. In particular, I argue that according to my account of reduction-as-construction, there are two suc- cessful examples of reduction. Thermodynamics reduces to statistical mechanics, and statistical mechanics reduces to the underlying microdynamics - be they quantum or classical. The reduction of a given theory alters that theory's scope, that is: its domain of applicability. The scope of thermodynamics will be central to this thesis - and I will argue for a narrower scope than some authors. This thesis consists of four Chapters, together with an introduction and a conclusion. In Chapter 1, I discuss how different levels of description relate to one another. I argue that a higher-level of description is reduced to the lower level, if the higher-level quantities and their behaviour can be constructed or captured by the lower-level theory. I claim that 'functionalism' can be helpful in securing reductions. In this Chapter I also argue that the aim of reduction is to vindicate, not eliminate, the higher-level theory. In Chapter 2, I tackle the reduction of thermodynamics to statistical mechanics. I articulate the functional, or nomological, role of various thermodynamic quantities that are implicitly defined by the zeroth, first and second laws of thermodynamics: temperature, energy and entropy respectively. I then argue that there are quantities in statistical mechanics that realise these roles: though finding them sometimes requires us to focus on quantum, rather than classical, statistical mechanics. In Chapter 3, I consider the reductive relationship between statistical mechanics and the underlying microdynamics. I demonstrate how the irreversible equations of statistical mechanics can be constructed from the underlying microdynamics using what I label the 'Zwanzig-Zeh-Wallace' framework. Yet this framework uses a procedure called 'coarse-graining' which has been heavily criticised in the literature; so in this Chapter I offer a justification of coarse-graining. One upshot is that the time-asymmetry in statistical mechanics is weakly emergent. In Chapter 4, I consider a question about the domain of applicability of thermal physics. Namely: does it apply to self-gravitating systems, such as elliptical galaxies? Much controversy surrounds this question: some argue yes, others argue no. I deflate the dispute by claiming that thermodynamics does not apply, but statistical mechanics does. Thus, my delineation of thermodynamics and statistical mechanics earlier in this thesis not only makes headway with the question of reduction, but also sheds light on this dispute. I argue that this situation - statistical mechanics, but without thermodynamics - can be understood in terms of a central notion in thermal physics: the thermodynamic limit. But as I also discuss: justifying this idealisation has been philosophically controversial.

This thesis concerns the metaphysics of scale. It investigates the implications of a physical determinable being dimensionful. In particular, it considers the case study of mass, as it features within Newtonian Gravity. Nevertheless, most of the terminology, methodology and arguments developed should be relatively straightforwardly applicable to other determinables and theories. Weak Absolutism about mass holds that mass ratios obtain in virtue of absolute masses. Weak Comparativism denies this. In the first five chapters I argue in favour of Weak Absolutism over Weak Comparativism. The sixth chapter argues against reducing mass to other non-mass facts. The overall conclusion is Strong Absolutism about mass within Newtonian Gravity: mass ratios obtain in virtue of absolute masses, which themselves are fundamental (i.e. they do not require anything further in order to obtain). Comparativism promises to recover all the virtues of absolutism, in particular its empirical adequacy, but at a lower 'metaphysical cost'. Special attention is given to Dasgupta's recent comparativist proposal. Dasgupta interprets the requirement of empirical adequacy in terms of the undetectability of the absolute mass scale. I argue that undetectability is an unsuitable way of understanding empirical adequacy and that we would do better to understand it in terms of a theory's ability to correctly generate the set of empirically possible worlds (or at least the actual world). I refute Dasgupta's comparativism both on my terms and on his own terms. I subsequently develop and strongly criticise alternative versions of comparativism. Chapter five sheds doubt on the supposed 'metaphysical parsimony' of comparativism. This debate should be of particular interest to readers who engage with the substantivalism-relationalism debate. These debates are much more entwined than previously acknowledged, which provides a significant source of mutual inspiration, although I do also draw out some important disanalogies.

Esta tese explora tópicos de Filosofia da Mecânica Estatística e sua inserção no Ensino de Física. Levanta-se inicialmente a discussão filosófica entre o reducionismo e o emergentismo. Esta questão permeia os debates científicos em Mecânica Estatística e em outras áreas, mas costuma ficar fora dos currículos escolares e universitários. Defendemos que esta discussão tem grande valor educacional para a formação do futuro professor e dos futuros cidadãos, mostrando como a ciência de fato é construída, e revelando aspectos da ciência para os quais não há uma visão de consenso único. Além disso, a natureza de modelos e aproximações foi estudada, sendo explorados diversos modelos de Mecânica Estatística, visando seu uso em sala de aula. Ao final da tese, apresenta-se uma proposta de curso onde essas questões poderão ser discutidas em sala de aula, contribuindo para um enriquecimento dos estudos sobre a Natureza da Ciência. / This thesis explores topics in the Philosophy of Statistical Mechanics and their use in Physics Teaching. It begins with the philosophical discussion between reductionism and emergentism. This issue is present in the scientific debates in Statistical Mechanics and other fields, but is usually not treated in high school and university courses. We argue that this discussion has great educational value for the future teachers and citizens, showing how science is constructed and revealing aspects of science about which there isn\'t a consensus. The nature of models and approximations is also studied, and various models in Statistical Mechanics are explored, in connection to their use in the classroom. At the end, a proposal for a course syllabus is presented, in which the issues explored in this thesis can be discussed in the classroom, contributing to the enrichment of the studies on the Nature of Science.

Quantum theory describes our universe incredibly successfully. To our classically-inclined brains, however, it is a bizarre description that requires a reimagining of what fundamental reality, or 'ontology', could look like. This thesis examines different ontological features in light of the success of quantum theory, what it requires, and what it rules out. While these investigations are primarily foundational, they also have relevance to quantum information, quantum communication, and experiments on quantum systems. The way that quantum theory describes the state of a system is one of its most unintuitive features. It is natural, therefore, to ask whether a similarly strange description of states is required on an ontological level. This thesis proves that almost all quantum superposition states for d > 3 dimensions must be real - that is, present in the ontology in a well-defined sense. This is a strong requirement which prevents intuitive explanations of the many quantum phenomena which are based on superpositions. A new theorem is also presented showing that quantum theory is incompatible with macro-realist ontologies, where certain physical quantities must always have definite values. This improves on the Leggett-Garg argument, which also aims to prove incompatibility with macro-realism but contains loopholes. Variations on both of these results that are error-tolerant (and therefore amenable to experimentation) are presented, as well as numerous related theorems showing that the ontology of quantum states must be somewhat similar to the quantum states themselves in various specific ways. Extending these same methods to quantum communication, a simple proof is found showing that an exponential number of classical bits are required to communicate a linear number of qubits. That is, classical systems are exponentially bad at storing quantum data. Causal influences are another part of ontology where quantum theory demands a revision of our classical notions. This follows from the outcomes of Bell experiments, as rigorously shown in recent analyses. Here, the task of constructing a native quantum framework for reasoning about causal influences is tackled. This is done by first analysing the simple example of a common cause, from which a quantum version of Reichenbach's principle is identified. This quantum principle relies on an identification of quantum conditional independence which can be defined in four ways, each naturally generalising a corresponding definition for classical conditional independence. Not only does this allow one to reason about common causes in a quantum experiments, but it can also be generalised to a full framework of quantum causal models (mirroring how classical causal models generalise Reichenbach's principle). This new definition of quantum causal models is illustrated by examples and strengthened by it's foundation on a robust quantum Reichenbach's principle. An unusual, but surprisingly fruitful, setting for considering quantum ontology is found by considering time travel to the past. This provides a testbed for different ontological concepts in quantum theory and new ways to compare classical and quantum frameworks. It is especially useful for comparing computational properties. In particular, time travel introduces non-linearity to quantum theory, which brings (sometimes implicit) ontological assumptions to the fore while introducing strange new abilities. Here, a model for quantum time travel is presented which arguably has fewer objectionable features than previous attempts, while remaining similarly well-motivated. This model is discussed and compared with previous quantum models, as well as with the classical case. Together, these threads of investigation develop a better understanding of how quantum theory affects possible ontologies and how ontological prejudices influence quantum theory.

Submitted by Luciana Ferreira (lucgeral@gmail.com) on 2018-08-06T11:33:35Z No. of bitstreams: 2 Dissertação - Igor Souza Saraiva - 2017.pdf: 943933 bytes, checksum: 267b2481555b7b8f95c12f6f3c5967ce (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2018-08-06T11:50:50Z (GMT) No. of bitstreams: 2 Dissertação - Igor Souza Saraiva - 2017.pdf: 943933 bytes, checksum: 267b2481555b7b8f95c12f6f3c5967ce (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2018-08-06T11:50:50Z (GMT). No. of bitstreams: 2 Dissertação - Igor Souza Saraiva - 2017.pdf: 943933 bytes, checksum: 267b2481555b7b8f95c12f6f3c5967ce (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2018-07-16 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / In this dissertation, we propose a philosophical discussion about some assumptions and consequences of the relativity principles embodied by physical theories. In the first chapter we start by suggesting on the first chapter a general vision of the logical structure of a class of space-time theories so wide that covers not only Newtonian mechanics but also special and general relativity. The relativity principle that is satisfied by each one of these theories appears as a consequence of a the transformation group which characterizes the physical equivalence relationship between space-time structures inside the theory. Such group is called “symmetry group” and is also responsible of establishing the general rule of permutation between frames of reference allowed by the theory. In the second and third chapter we will use these ideas to contrast and inspect key properties of the three mentioned theories. Our goal is to finish with an analysis of the philosophical significance of the principle of general relativity and its exact relation to the others pertinent principles of general relativity theory. / Nesta dissertação, propomos uma discussão filosófica acerca de alguns pressupostos e consequências dos princípios de relatividade que são satisfeitos pelas teorias físicas. Começamos propondo, no primeiro capítulo, uma visão geral da estrutura lógica de uma classe de teorias do espaço-tempo ampla o suficiente para abranger tanto a mecânica deNewton, quanto a relatividade restrita e a relatividade geral. O princípio de relatividade que é satisfeito por cada uma dessas teorias aparece como uma consequência do grupo de transformações que caracteriza as relações de equivalência física entre as estruturas espaçotemporais dentro da teoria. Tal grupo de transformações, que denominamos de “grupo simetria”, também é responsável por determinar a regra de tradução entre os quadros de referência que as teorias permitem. No segundo e terceiro capítulo usaremos essas ideias para contrastar e examinar propriedades centrais das três teorias que são examinadas neste trabalho. Nosso objetivo é chegar ao final da dissertação com uma análise da significância filosófica do princípio de relatividade geral e sua exata relação para com outros princípios pertinentes a teoria geral da relatividade.

Esta tese explora tópicos de Filosofia da Mecânica Estatística e sua inserção no Ensino de Física. Levanta-se inicialmente a discussão filosófica entre o reducionismo e o emergentismo. Esta questão permeia os debates científicos em Mecânica Estatística e em outras áreas, mas costuma ficar fora dos currículos escolares e universitários. Defendemos que esta discussão tem grande valor educacional para a formação do futuro professor e dos futuros cidadãos, mostrando como a ciência de fato é construída, e revelando aspectos da ciência para os quais não há uma visão de consenso único. Além disso, a natureza de modelos e aproximações foi estudada, sendo explorados diversos modelos de Mecânica Estatística, visando seu uso em sala de aula. Ao final da tese, apresenta-se uma proposta de curso onde essas questões poderão ser discutidas em sala de aula, contribuindo para um enriquecimento dos estudos sobre a Natureza da Ciência. / This thesis explores topics in the Philosophy of Statistical Mechanics and their use in Physics Teaching. It begins with the philosophical discussion between reductionism and emergentism. This issue is present in the scientific debates in Statistical Mechanics and other fields, but is usually not treated in high school and university courses. We argue that this discussion has great educational value for the future teachers and citizens, showing how science is constructed and revealing aspects of science about which there isn\'t a consensus. The nature of models and approximations is also studied, and various models in Statistical Mechanics are explored, in connection to their use in the classroom. At the end, a proposal for a course syllabus is presented, in which the issues explored in this thesis can be discussed in the classroom, contributing to the enrichment of the studies on the Nature of Science.

A number of philosophical questions, all connected to modern research in quantum gravity, are discussed in this dissertation. The goal of research in quantum gravity is to find a quantum theory for gravitation; the other fundamental forces are already understood in terms of quantum physics. Quantum gravity is studied within a number of different research programmes. The most popular are string theory and loop quantum gravity; besides these a number of other approaches are pursued. Due to the lack of empirical support, it is relevant to assess the scientific status of this research. This is done from four different points of view, namely the ones held by: logical positivists, Popper, Kuhn and Lakatos. It is then argued that research in quantum gravity may be considered scientific, conditional on scientists being open with the tentative and speculative nature of their pursuits. Given the lack of empirical progress, in all approaches to quantum gravity, a pluralistic strategy is advised. In string theory there are different theoretical formulations, or dualities, which are physically equivalent. This is relevant for the problem of underdetermination of theories by data, and the debate on scientific realism. Different views on the dualities are possible. It is argued that a more empiricist view on the semantics of theories, than what has been popular lately, ought to be adopted. This is of importance for our understanding of what the theories tell us about space and time. In physics and philosophy, the idea that there are worlds or universes other than our own, has appeared in different contexts. It is discussed how we should understand these different suggestions; how they are similar and how they are different. A discussion on, how and when theoretical multiverse scenarios can be empirically testable, is also given. The reliability of thought experiments in physics in general and in quantum gravity in particular is evaluated. Thought experiments can be important for heuristic purposes, but in the case of quantum gravity, conclusions based on thoght experiments are not very reliable.

[pt] Esta investigação tem por objetivo apresentar um modelo de cooperação entre filosofia e ciência experimental, por meio de um domínio comum, a matemática, especialmente a álgebra. Essa coordenação entre dois domínios situados em níveis distintos de conhecimento da realidade natural chama-se filosofia da natureza, e havia sido proposta por Aristóteles nos oito livros da Física. Com o advento da ciência experimental moderna entre os séculos XVI e XVII, tal tipo de investigação passou a ter um caráter secundário, porquanto se entendeu que as teorias, especialmente as de base matemática, e o método experimental em conjunto seriam suficientes para dar conta da estrutura da realidade. No entanto, faz-se necessário -- e esta é nossa proposta --, em decorrência das questões de limite suscitadas pela própria ciência experimental, retomar uma investigação complementar à científica ou epistêmica, e coordenada com esta, de modo a prover um conhecimento integral, totalizante, da realidade natural. Portanto, analisa-se o alcance da ciência experimental quanto à compreensão científica da natureza da matéria, expondo certas limitações deste tipo de enfoque, tendo por base a epistemologia proposta pelo filósofo Jacques Maritain. Em seguida, analisa-se o estatuto metafísico ou ontológico da matéria, com base em vários textos de Tomás de Aquino, e propõe-se um modelo algébrico para a representação de elementos daquela ontologia. Por fim, apresentam-se algumas conseqüências que se podem extrair desse modelo, com vistas à compreensão de aspectos da realidade natural como espaço-tempo e movimento, não-localidade quântica, e uma proposta de visão totalizante da realidade física,denominada holomovimento, sugerida pelo físico David Bohm. / [en] The main purpose of this enquiry is to provide a cooperative framework for philosophy and experimental science. This should be accomplished by means of a common domain, namely mathematics, specifically through algebra. Such a coordination between two different levels of knowledge of the natural world is named philosophy of nature, and had been proposed by Aristotle in his eight book Physics. As an outcome of the rise of modern science between 16th and 17th centuries, this kind of enquiry has been left aside as a secondary enterprise. For it has been a common understanding that modern scientific theories together with experimental methods would suffice to account for the structure of reality.However, I shall propose that it is necessary -- as a consequence of edge research on experimental sciences -- to resume a complementary enquiry to the scientific (epistemic) research, in such a coordinated way with this latter as to provide a whole knowledge of the natural world. Thus, I shall analyze the concept of matter as it is understood by experimental science, and based upon Jacques Maritain´s proposed epistemology I shall present some of the shortcomings of scientific approach to matter. Shortly afterwards, I shall analyze the metaphysical (ontological) status of matter based upon several writings from Thomas Aquinas, and I shall propose an algebraic model to represent some of the ontological elements that build up matter from a metaphysical point of view. Lastly, I shall present some of the consequences that can be obtained from that model in order to gain a metaphysical understanding of physical aspects such as space-time and movement, quantum non-locality, and also a whole perspective of physical reality as proposed by David Bohm which he called holomovement.

There have been recent explosions of interest in two fields: Madhyamaka-Pyrrhonism parallels and Pyrrhonism itself, which seems to have been misunderstood and therefore neglected by the West for the same reasons and in the same ways that Madhyamaka traditionally has often been by the West and the East. Among these recent studies are several demonstrating that grounding in Madhyamaka, for example, reveals and illuminates the import and insights of Pyrrhonean arguments. Furthermore it has been suggested that of all European schools of philosophy Pyrrhonism is the one closest to Buddhism, and especially to Madhyamaka. Indeed Pyrrho is recorded to have studied with philosophers in Taxila, one of the first places where Madhyamaka later flourished, and the place where the founder of Madhyamaka, Nāgārjuna, may have received hitherto concealed texts which became the foundation for his school. In this dissertation I explore just how similar these two philosophical projects were. I systematically treat all the arguments in the Pyrrhonist redactor Sextus Empiricus’ Outlines of Pyrrhonism and Against Dogmatists and compare them to the most similar arguments available in the Madhyamaka treatises and related texts. On this basis, I ask whether the Pyrrhonists and the Buddhists would satisfy each other’s self-identifying criteria, or what characteristics would disqualify either or both in the other’s eyes. I also ask what questions arise from the linguistic and historical evidence for interactions between the Pyrrhonist school and the Madhyamaka school, and how sure we can be of the answers. Did Pyrrho learn Buddhism in Taxila? Was Nāgārjuna a Pyrrhonist? Finally I bring the insights of the living commentarial tradition of Madhyamaka to bear on current scholarly controversies in the field of Sextan Pyrrhonism, and apply the subtleties of interpretation of the latter which have developed in recent scholarship to Madhyamaka and its various difficulties of interpretation, to scrutinize each school under the illumination of the other. With this hopefully illuminated view, I address for example whether Sextus was consistent, whether living Pyrrhonism implies apraxia, whether Pyrrhonism is philosophy at all, and whether Madhyamaka is actually nihilism.