This dissertation explores philosophical issues that arise in the practice of contemporary particle physics. The first chapter is a historical sketch of how the particle physics community came to believe that the quantum field theories used in particle physics are best understood as effective field theories -- quantum field theories that become inapplicable at some short distance scale and incorporate this inevitable breakdown in their mathematical framework. The second chapter argues that, contrary to the claims of many philosophers, the unique mathematical resources and empirical successes of effective field theories means that they can and should be equipped with a realist interpretation. The third chapter turns to an issue that has been at the center of particle physics for the last 40 years, the problem of naturalness, and draws on the renormalization group to provide a univocal understanding of ``naturalness'' that can make sense of the way it is employed in physical practice. Finally in the fourth chapter I critically examine recent philosophical work which argues that different physical scales in quantum field theory enjoy a sense of autonomy, arguing that the formal results on which this recent work is based cannot support the conclusions with which they have been saddled.

I defend three general claims concerning inter-theoretic reduction in physics. First, the popular notion that a superseded theory in physics is generally a simple limit of the theory that supersedes it paints an oversimplified picture of reductive relations in physics. Second, where reduction specifically between two dynamical systems models of a single system is concerned, reduction requires the existence of a particular sort of function from the state space of the low-level (purportedly more accurate and encompassing) model to that of the high-level (purportedly less accurate and encompassing) model that approximately commutes, in a specific sense, with the rules of dynamical evolution prescribed by the models. The third point addresses a tension between, on the one hand, the frequent need to take into account system-specific details in providing a full derivation of the high-level theory’s success in a particular context, and, on the other hand, a desire to understand the general mechanisms and results that under- write reduction between two theories across a wide and disparate range of different systems; I suggest a reconciliation based on the use of partial proofs of reduction, designed to reveal these general mechanisms of reduction at work across a range of systems, while leaving certain gaps to be filled in on the basis of system-specific details. After discussing these points of general methodology, I go on to demonstrate their application to a number of particular inter-theory reductions in physics involving quantum theory. I consider three reductions: first, connecting classical mechanics and non-relativistic quantum mechanics; second,connecting classical electrodynamics and quantum electrodynamics; and third, connecting non-relativistic quantum mechanics and quantum electrodynamics. I approach these reductions from a realist perspective, and for this reason consider two realist interpretations of quantum theory - the Everett and Bohm theories - as potential bases for these reductions. Nevertheless, many of the technical results concerning these reductions pertain also more generally to the bare, uninterpreted formalism of quantum theory. Throughout my analysis, I make the application of the general methodological claims of the thesis explicit, so as to provide concrete illustration of their validity.

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.

Shaped pulses can be used for uniform spin-1 excitation. The effects of the pulses on spin-1 excitation is seen as distortion of two types: phase distortions and amplitude distortions. By reducing the distortions a spin-1 excitation becomes more uniform. In the case of time-symmetric shaped pulses, spin-1 excitation is free of phase distortions. The spin-1 excitation in that case can be made uniform over a larger frequency bandwidth. The number of possible shaped pulses is so large that a computer-aided search is needed to find the desirable shaped pulses. A theoretical analysis is used to find the connection between a shaped pulse and the corresponding spin-1 excitation. The theoretical analysis in density matrix formalism gives the spin-1 excitation in closed-form expressions that are too complicated. In such a case the connection between a shpaed pulse and spin-1 excitation is not straightforward. A brute-force search for a desirable shaped pulse can consume too much computer time and thus time the scope of the search. By using the formalism of quaternions in the theoretical analysis, spin-1 excitation is presented in simple closed form expressions. It is then shown tht if the choice is limited to time-symmetric shaped pulses then these closed form expressions become much simpler. It is also shown that a spin-1 excitation is free of phase distortions in that case. These simple closed form expressions can be used as the building blocks of a much more concise program code for the computer aided search. As a result a computer aided search for a desirable shaped pulse becomes much faster in speed and larger in scope. More shaped pulses for improved spin-1 can be found. / xiii, 99 leaves : ill. ; 28 cm.

Orientador: Jairo Jose da Silva / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Filosofia e Ciencias Humanas / Made available in DSpace on 2018-08-10T16:01:58Z (GMT). No. of bitstreams: 1 Bassani_DouglasAntonio_D.pdf: 770300 bytes, checksum: 79e160f3634bdee36d2d52581fd9263d (MD5) Previous issue date: 2008 / Resumo: Este trabalho visa apresentar e analisar os fundamentos da concepção operacional de significado proposta por P. W. Bridgman (1881-1965). Começo com o operacionalismo na Física, onde se originou, como tentativa de solução de problemas nos fundamentos. Trato da questão da consistência com a experiência dos conceitos, afirmações e teorias da Física. Em seguida, analiso o operacionalismo na Lógica, na Lógica aplicada em contextos físicos e em contextos matemáticos. Apresento o problema do princípio do terceiro excluído e o papel da verificação das afirmações e das verdades nesse contexto. Essas análises explicitam a proximidade do operacionalismo com o intuicionismo de Brouwer em filosofia da matemática. As conseqüências disso e o caráter operacional da matemática serão detalhadamente abordados no trabalho / Abstract: This paper aims to present and analyze the basis of the operational conception of the meaning proposed by P. W. Bridgman (1881-1965). I begin with the operationalism in Physics, where it was first proposed, as a solution attempt to problems in the foundations. I deal with the question of the consistency with the experience of concepts, affirmations and theories of Physics. Then, I analyze the operationalism in Logic, in the Logic apply in physical contexts and in mathematical contexts. I consider the principle of the excluded middle and the role of the checking of the affirmations and the truths in relation with it. This analysis will render it explicit the proximity of operationalism with Brouwer's intuitionism in the philosophy of the mathematics. The consequences of operationalistic theses for mathematics and the alleged operational character of mathematics will be discussed in details in this paper / Doutorado / Filosofia / Doutor em Filosofia

Doctorat en philosophie et lettres / info:eu-repo/semantics/nonPublished

This thesis investigates the interplay between explanatory issues in special relativity and the theory's metaphysical foundations. Special attention is given to the 'dynamical approach' to relativity, promoted primarily by Harvey Brown and collaborators, according to which the symmetries of dynamical laws are explanatory of relativistic effects, inertial motion, and even the Minkowskian geometrical structure of a specially relativistic world. The thesis begins with a review of Einstein's 1905 introduction to special relativity, after which brief historical introductions are given for the standard 'geometrical' approach to relativity and the unorthodox 'dynamical' approach. After a critical review of recent literature on the topic, the dynamical approach is shown to be in need of a metaphysical package that would undergird the explanatory claims mentioned above. It is argued that the dynamical approach is best understood as a form of relationalism - in particular, as a relativistic form of 'regularity relationalism', promoted recently by Nick Huggett. According to this view, some portion of a world's geometrical structure actually supervenes upon the symmetries of the best-system dynamical laws for a material ontology endowed with a primitive sub-metrical structure. To explore the plausibility of this construal of the dynamical approach, a case study is carried out on solutions to the Klein-Gordon equation. Examples are found for which the field values, when purged of all spatiotemporal structure but their induced topology, are still arguably best-systematized by the Klein-Gordon equation itself. This bolsters the plausibility of the claim that some system of field values, endowed with mere sub-metrical structure, might have as its best-systems dynamical laws a (set of) Lorentz-covariant equation(s), on which Minkowski geometrical structure would supervene. The upshot is that the dynamical approach to special relativity can be defended as what might be called an ontologically and ideologically relationalist approach to Minkowski spacetime structure. The chapters refer regularly to three appendices, which include a brief introduction to topological and differentiable spaces.

In this dissertation I analyze Sir Arthur Eddington's statistical theory as developed in the first six chapters of his posthumously published Fundamental Theory. In particular I look at the mathematical structure, philosophical implications, and relevancy to modern physics. This analysis is the only one of Fundamental Theory that compares it to modern quantum field theory and is the most comprehensive look at his statistical theory in four decades. Several major insights have been made in this analysis including the fact that he was able to derive Pauli's Exclusion Principle in part from Heisenberg's Uncertainty Principle. In addition the most profound general conclusion of this research is that Fundamental Theory is, in fact, an early quantum field theory, something that has never before been suggested. Contrary to the majority of historical reports and some comments by his contemporaries, this analysis shows that Eddington's later work is neither mystical nor was it that far from mainstream when it was published. My research reveals numerous profoundly deep ideas that were ahead of their time when Fundamental Theory was developed, but that have significant applicability at present. As such this analysis presents several important questions to be considered by modern philosophers of science, physicists, mathematicians, and historians. In addition it sheds new light on Eddington as a scientist and mathematician, in part indicating that his marginalization has been largely unwarranted.

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