Dissertations / Theses on the topic 'Quantum theory – Philosophy'

This thesis is a contribution to the debate on the implications of quantum information theory for the foundational problems of quantum mechanics. In Part I an attempt is made to shed some light on the nature of information and quantum information theory. It is emphasized that the everyday notion of information is to be firmly distinguished from the technical notions arising in information theory; however it is maintained that in both settings ‘information’ functions as an abstract noun, hence does not refer to a particular or substance. The popular claim ‘Information is Physical’ is assessed and it is argued that this proposition faces a destructive dilemma. Accordingly, the slogan may not be understood as an ontological claim, but at best, as a methodological one. A novel argument is provided against Dretske’s (1981) attempt to base a semantic notion of information on ideas from information theory. The function of various measures of information content for quantum systems is explored and the applicability of the Shannon information in the quantum context maintained against the challenge of Brukner and Zeilinger (2001). The phenomenon of quantum teleportation is then explored as a case study serving to emphasize the value of recognising the logical status of ‘information’ as an abstract noun: it is argued that the conceptual puzzles often associated with this phenomenon result from the familiar error of hypostatizing an abstract noun. The approach of Deutsch and Hayden (2000) to the questions of locality and information flow in entangled quantum systems is assessed. It is suggested that the approach suffers from an equivocation between a conservative and an ontological reading; and the differing implications of each is examined. Some results are presented on the characterization of entanglement in the Deutsch-Hayden formalism. Part I closes with a discussion of some philosophical aspects of quantum computation. In particular, it is argued against Deutsch that the Church-Turing hypothesis is not underwritten by a physical principle, the Turing Principle. Some general morals are drawn concerning the nature of quantum information theory. In Part II, attention turns to the question of the implications of quantum information theory for our understanding of the meaning of the quantum formalism. Following some preliminary remarks, two particular information-theoretic approaches to the foundations of quantum mechanics are assessed in detail. It is argued that Zeilinger’s (1999) Foundational Principle is unsuccessful as a foundational principle for quantum mechanics. The information-theoretic characterization theorem of Clifton, Bub and Halvorson (2003) is assessed more favourably, but the generality of the approach is questioned and it is argued that the implications of the theorem for the traditional foundational problems in quantum mechanics remains obscure.

This thesis deals with the set of issues commonly known as the 'measurement problem' in quantum mechanics. The main thesis is that the problems are best understood as typically theoretical problems, in the sense that they are not problems directly concerned with the ability of the quantum theory to account for, or represent, actual measurements. This is contrary to the standard view that the quantum measurement problem is in fact about how to fit theory to experiment. I explain how I characterise a theoretical problem and argue against claims that quantum measurement theory is unrealistic or ineffective because it bears so little relation to actual measurement practice: I argue that the quantum theory's analysis of measurement need not be committed to doing for the experimenter what Henry Margenau and other critics think it should do. Its principal aim is to answer two questions. First, it tells us what properties are to be associated to quantum states; secondly, it tells us what, in the theory, a measurement must be if these properties are to emerge. I then discuss some of the specific aspects of the problem of measurement, in particular the results known as insolubility proofs of the quantum measurement problem and the characterisation of the quantum measurement interactions satisfying standard probabilistic constraints. I prove several results here, amongst them characterisations of all interactions jointly satisfying the conditions of unitarity and, first, objectification, then secondly, probability reproducibility conditions. These are the standard conditions which capture our intuitions about quantum measurement. I show how the results lead to negative consequences with respect to the interpretive questions in quantum mechanics. The discussion of these specific aspects of quantum measurements does, on the other hand, suggest a particular strategy for solving the problems. This is found in Arthur Fine's solution to the measurement problem, which is based on the idea of a selective interaction. The discussion of Fine's solution emphasises in general how simply implementing technical strategies is not sufficient to solve the measurement problem in quantum mechanics: further arguments must be given for why the strategy is appropriate, rather than just mathematically satisfactory. I claim that the arguments given by Fine are far from sufficient. The thesis concludes that, although the quantum theory of measurement is immune from Margenau's critique, and retains a theoretical autonomy, it is still plagued by numerous problems: the thesis identifies clearly what some of these problems are and considers some solutions, most of which, however, raise serious philosophical questions about the interpretation of quantum mechanics.

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.

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.

Thesis (Ph. D.)--Indiana University, Dept. of History and Philosophy of Science, 2006.
"Title from dissertation home page (viewed July 16, 2007)." Source: Dissertation Abstracts International, Volume: 67-10, Section: A, page: 3842. Advisers: Jordi Cat; Michael Dickson.

This thesis compares the concepts presented in the Seventeenth Discussion of al-Ghazali's Tahafut al-Falasifa with concepts currently being discussed in the field of quantum physics. Written as an attack on the neo-Platonic and Aristotelian thinking which challenged the orthodox theology of Medieval Islam, Tahafut al-Falasifa (Incoherence of the Philosophers) questions the understanding of physical reality forwarded by the philosophers of al-Ghazali's times. The Seventeenth Discussion ('On causality and miracles') in particular, with its aim of proving the possibility of miracles, questions the acceptance of notions such as necessary causality and the validity of scientific observation in the natural world.
Although several scholars have examined al-Ghazali's argument in the Seventeenth Discussion in terms of causality, observation and the nature of human conceptions of physical reality, and many others have noted the implicit potential connections between quantum theory and concepts of religiosity, only one, Karen Harding, has attempted a synthesis of the ideas put forth within these two seemingly diverse subjects. This thesis, then, carries forward from the ideas of Harding and attempts an original comparative analysis of the two. (Abstract shortened by UMI.)

Scientific realists and non-realists disagree over the reach of scientific knowledge: does it extend beyond the observational realm. Intuitions about abductive inferences are at the heart of many realist positions, but are brought into question by the non-realists' contention that theories are underdetermined by data, and the alleged circularity of realist attempts to show that such inferences are reliable. Some realists have tried to circumvent this problem by constructing methodological arguments for realism: if realism is embedded in scientific practice, the realist's picture of science might provide the best explanation of scientific success. Some non-realists reply by again pointing to the circularity of this strategy, which relies, again, on an abductive inference. Others deny that scientists do adopt realist stances. A methodological realist position is constructed: realist constraints on the acceptance and pursuit of theories-for instance requirements of intertheoretic coherence, and the avoidance of ad hoc explanation-have often contributed to progress in science. The position is immune to non-realist worries about the circularity of realist arguments, for it is a thesis about how science is practised, not the kind of knowledge it provides. The argument is pursued within a diachronic account of theory appraisal: Imre Lakatos' methodology of scientific research programmes (MSRP) examines the principles that govern the construction of theories, and provides criteria-achievement of progress-for the appraisal of research programmes. Although Lakatos may have seen these selection criteria, when fulfilled, as symptoms of something else-the fulfilment in the theory's development of some ideal of scientific honesty-achievement of Lakatosian progress can Serve as an end in itself. The realist methods mentioned in the last paragraph are then appraised as means to this end. Since the position has a methodological formulation and background, it is applied as a historical thesis to case studies in line with Lakatos' metamethodology. These comprise two explanatory forays into history: the consistency of Bohr's 1913 model of the atom, and the construction by Heisenberg and Schrodinger of the two original formulations of quantum mechanics. There follows one contemporary application: the construction of explanations in quantum chemistry using approximate models of molecules.

This thesis employs perspectives inspired by General Systems Theory to address issues in philosophy, including moral philosophy and philosophy of mind. I present an overview of a range of ideas from the study of physical systems that may be used to provide a firm physicalist foundation to explorations of some common questions in philosophy. I divide these topics into three categories: the Physical Category, the Relevance Category and the Signal Elements Category. I interpret concepts from General Systems Theory, including information and entropy, in a way that I believe facilitates their incorporation into philosophical discussion. I also explain various points arising from General Systems Theory, such as order and disorder, stability, complexity, and self-organisation, and show how ideas from these areas can be applied to certain philosophical problems. I explain relevance in terms of stability, in order to link these scientific perspectives to questions in moral philosophy. I suggest a possible physical foundation for a theory of morality, which takes the form of a variety of Utilitarianism, intended to balance the competing needs of open systems to manage entropy. Such a theory of morality must be capable of dealing with limitations arising from the physicality of information; I propose game theory as a solution to this problem. This thesis also covers issues connected to the above points regarding the nature of consciousness and communication. In particular, I examine the role of linguistic associations in consciousness; and some related features of language and other non-linear representational schemes.

In this thesis I discuss the nature of ‘measurement’ in quantum theory. ‘Measurement’ is associated with several different processes: the gradual imprinting of information about one system onto another, which is well understood; the collapse of the wavefunction, which is ill-defined and troublesome; and finally, the means by which inferences about unknown experimental parameters are made. I present a theoretical extension to an experimental proposal from Leggett and Garg, who suggested that the quantum-or-classical reality of a macroscopic system may be probed with successive measurements arrayed in time. The extension allows for a finite level of imperfection in the protocol, and makes use of Leggett’s ‘null result’ measurement scheme. I present the results of an experiment conducted in Oxford that, up to certain loopholes, defies a non-quantum interpretation of the dynamics of phosphorous nuclei embedded in silicon. I also present the theory of statistical parameter estimation, and discover that a recent trend to employ time symmetric ‘postselected’ measurements offers no true advantage over standard methods. The technique, known as weak-value amplification, combines a weak transfer of quantum information from system to meter with conditional data rejection, to surprising effect. The Fisher information is a powerful tool for evaluating the performance of any parameter estimation model, and it reveals the technique to be worse than ordinary, preselected only measurements. That this is true despite the presence of noise (including magnetic field fluctuations causing deco- herence, poor resolution detection, and random displacements), casts serious doubt on the utility of the method.

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.

Science is curiosity about the natural world translated into knowledge; it serves to identify laws and validate hypotheses. The quest for knowledge is influenced by the paradigm of the scientist. The primary object of this study is to examine Quantum Mechanics and Sacred/Native science for similarities and differences. This will be accomplished through an extensive use of authorities from both Western and Native sciences in an in depth examination of the paradigms upon which their foundations are based. This study will explore language and how language used leads the scientist down a particular pathway. This study will conclude in a summary fashion, an exploration of a few select key concepts from both Native and Western sciences from a comparative perspective.
ix, 135 leaves ; 29 cm.

This dissertation's purpose is to test the hypothesis that beliefs in the possibility of post-mortem survival can be rationally held within the context of the contemporary scientific and philosophical environment. In terms of criteria of rationality, a basic evidentialism is assumed, such that propositions which are sufficiently supported by the available evidence can be rationally held. With regard to the compatibility with contemporary science and philosophy, it follows as a further criterion that the relevant evidence must be satisfactorily anchored within the framework of these traditions. The relevant evidence concerns two levels. First, the basic level of the conceptual coherence of afterlife beliefs is addressed, so that the logical possibility of post-mortem survival can be established. Secondly, the viability of the metaphysics which are implied in the support of the logical possibility (i.e. the metaphysics needed to actualize post-mortem survival) is defended, establishing the metaphysical possibility of post-mortem survival. At this stage, reductive physicalism, which is the only position that effectively undermines post-mortem survival, is criticized, and the problem of interaction which burdens several of the survival-enabling ontologies is addressed. As for the criterion of scientific compatibility, it is further shown that contemporary physics are compatible with the survival-enabling metaphysics, and that contemporary physics can be argued to provide a moderate positive relevance with regard to these positions. The conclusion drawn is that belief in the possibility of post-mortem survival is not only rationally permissible within the framework of contemporary science and philosophy, but also rationally obligatory, i.e. that this possibility cannot rationally be denied with regard to the reviewed evidence.

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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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Nessa investigação nos concentraremos no período de consolidação da teoria quântica, sobretudo naquilo que toca o livro A Lógica da Pesquisa Científica, de 1934. O centro da investigação é à crítica de Popper ao pensamento indutivista e subjetivista de Heisenberg, que por meio de considerações da filosofia da linguagem e com o apoio de defensores da filosofia positivista, construiu com outros partidários da chamada Interpretação de Copenhague a interpretação hegemônica da teoria quântica. O dedutivismo realista de Popper , apresentado no livro Lógica da Pesquisa Científica, visa combater essa visão, através de uma defesa da objetividade e do realismo que escapou dos limites da Epistemologia e ganhou ares éticos. Popper defendeu a Interpretação Estatística, que é um ramo da teoria corpuscular. Demonstraremos como que a interpretação acerca do alcance da Epistemologia opõe esses pensadores. Para Heisenberg a objetividade devia ser deixada de lado, a partir da constatação empírica do Princípio de Incerteza. O método científico deve, segundo o físico alemão, limitar os conceitos da linguagem clássica e aplica-los nas descrições dos fenômenos quânticos segundo as limitações operacionais dos conceitos. Para Popper, a metodologia dispensa questões linguísticas e apreende o método científico como sendo baseado na testabilidade, o que impõe que a análise epistemológica seja feita somente após a teoria ter sido conjecturada. Investigaremos a partir do pensamento de Popper e veremos como sua defesa do falseacionismo impõe uma interpretação da teoria quântica diferente daquela preconizada por Heisenberg.
In this investigation we will focus on the period of consolidation of the quantum theory, specially, on what concerns the book Logic of Scientific Discovery, of 1934. The center of this investigation is the Popper‟s critics to the inductivism and subjectivism of Heisenberg thought that, through concepts of the philosophy of language and the support of positivist philosophy advocates, built with other supporters of Copenhagen Interpretation, the hegemonic interpretation of quantum theory. The realistic deductivism of Popper, submitted in the Logic of Scientific Discovery, aim to tackle this position, through a defense of objectivity and realism that pushed the boundaries of epistemology and acquired ethical air. Popper supported the statistical interpretation of quantum theory, a branch of corpuscular interpretation. We will show how the interpretation of the epistemological range opposes these thinkers. To Heisenberg the objectivity must be set apart from the empirical realization of the Principle of Uncertainty. The scientific method, according to the German physicist, must limit the concepts of classical language and apply them in the quantum phenomena descriptions according to the operational limitations of concepts. According to Popper, the methodology exempts linguistic questions and perceives the scientific method as grounded on testability, which imposes that the epistemological analysis has to be made only after the theory has been conjectured. We will investigate from the thought of Popper and we will see how his defense of falseacionism imposes an interpretation of the quantum theory different from those preconized by Heisenberg.

Durant ces dernières décennies, la communauté informatique a montré un intérêt grandissant pour les modèles de calcul non-standard, inspirés par des phénomènes physiques, biologiques ou chimiques. Les propriétés exactes de ces modèles ont parfois été l'objet de controverses: que calculent-ils? Et à quelle vitesse? Les enjeux de ces questions sont renforcés par la possibilité que certains de ces modèles pourraient transgresser les limites acceptées du calcul, en violant soit la thèse de Church-Turing soit la thèse de Church-Turing étendue. La possibilité de réaliser physiquement ces modèles a notamment été au coeur des débats. Ainsi, des considérations empiriques semblent introduites dans les fondements même de la calculabilité et de la complexité computationnelle, deux théories qui auraient été précédemment considérées comme des parties purement a priori de la logique et de l'informatique. Par conséquent, ce travail est consacré à la question suivante : les limites du calcul reposent-elles sur des fondements empiriques? Et si oui, quels sont-ils? Pour ce faire, nous examinons tout d'abord la signification précise des limites du calcul, et articulons une conception épistémique du calcul, permettant la comparaison des modèles les plus variés. Nous répondrons à la première question par l'affirmative, grâce à un examen détaillé des débats entourant la faisabilité des modèles non-standard. Enfin, nous montrerons les incertitudes entourant la deuxième question dans l'état actuel de la recherche, en montrant les difficultés de la traduction des concepts computationnels en limites physiques
Recent years have seen a surge in the interest for non-standard computational models, inspired by physical, biological or chemical phenomena. The exact properties of some of these models have been a topic of somewhat heated discussion: what do they compute? And how fast do they compute? The stakes of these questions were heightened by the claim that these models would violate the accepted limits of computation, by violating the Church-Turing Thesis or the Extended Church-Turing Thesis. To answer these questions, the physical realizability of some of those models - or lack thereof - has often been put at the center of the argument. It thus seems that empirical considerations have been introduced into the very foundations of computability and computational complexity theory, both subjects that would have been previously considered purely a priori parts of logic and computer science. Consequently, this dissertation is dedicated to the following question: do computability and computational complexity theory rest on empirical foundations? If yes, what are these foundations? We will first examine the precise meaning of those limits of computation, and articulate a philosophical conception of computation able to make sense of this variety of models. We then answer the first question by the affirmative, through a careful examination of current debates around non-standard models. We show the various difficulties surrounding the second question, and study how they stem from the complex translation of computational concepts into physical limitations

Thesis (MA)--Stellenbosch University, 2003.
ENGLISH ABSTRACT: The advent of the computer age has seen many fundamental changes in the economics. The ease with which organisations can store and transmit information in unprecedented quantities and speeds has changed the face of the economy as well as the way in which organisations conduct their day to day operations. Information has become the primary resource for organisational competitiveness and this has seen an increasing drive for efficient information generation and management in an economy that is interconnected on a global scale. The demand for better information management practices is driven by the realisation that the global economy is susceptible to sudden and unpredictable changes that can potentially have global consequences. The more information organisations have at their disposal, the better their chances are of remaining competitive and relevant in the global economy. The informational economy confronts organisations with two very significant problems, the first is information overload due to the sheer volume of information that is available to them. The second problem is that despite the volume of available information organisations still are not privy to all the information that is required to lessen the impact of uncertainty that is so characteristic of the global economy. Organisations therefore always run the' risk of becoming irrelevant if they do not change constantly. This drive for continuous change and the dependence on information has led some organisational theorists and economists to compare the global economy and organisations to nonlinear systems found in nature. Examples of nonlinear systems are living organisms, ecologies and solar systems. All of these systems are characterised by high levels of interconnectedness and interdependence among individual units within a shared environment, which they co-create. Nonlinear systems are of particular interest to organisational theorists because these systems process information about the environment to adapt in an unpredictable way to unpredictable changes. Such systems are incredibly resilient because they are able to learn and adapt to different conditions. Another notable aspect of nonlinear systems is the clear structured and complex organisation that they exhibit in the absence of centralised control mechanisms. Every unit has the liberty to experiment with new designs and from the success of individual units an organised and stable system emerges with a strong link between the success of individuals and the whole system. The order that exists within nonlinear systems is known as self-organisation because it is not superimposed but emerges instead in a spontaneous manner. Nonlinear systems are therefore more than just the sum of their parts. The notion of nonlinear systems and self-organisation has seen authors such as Stacey, Wheatley and Senge develop new ideas about organisational development, leadership and organisational strategic thinking. Their ideas are based on what is popularly known as 'The New Science'. These ideas attempt to encourage organisations realise that the global economy functions as a nonlinear system and that organisations stand a better chance of success if they learn to understand the principles of nonlinear systems and to utilise the inherent creative and organising characteristics of such systems.
AFRIKAANSE OPSOMMING: Die aanvang van die rekenaar era het verskeie fundamentele veranderinge in ekonomie mee gebring. Die gemak en snelheid waarmee organisasies informasie kan stoor en versprei is ongekend en het terselfde tyd die voorkoms van die ekonomie verander asook die wyse waarop organisasies op 'n daaglikse basis funksioneer. Informasie het die belangrikste hulpbron geword vir organisasies in terme van kompetering en dit het 'n groter dryfkrag vir doeltreffende informasie ontginning en bestuur mee gebring in 'n ekonomie wat op 'n wereldwye skaal in mekaar gevleg is. Die aanvraag vir beter informasie bestuur praktyke word gedryf deur die wete dat die wereld ekonomie vatbaar is vir skielike en onvoorspelbare veranderinge wat potensieel 'n wereldwye impak kan he. Hoe meer informasie organisasies tot hul beskikking het hoe beter is hul kans om relevant en kompeterend te bly in die wereld ekonomie. Die informasie ekonomie konfronteer organisasies met twee fundamentele probleme. Die eerste gevaar is dat organisasies oorlaai kan word met informasie as gevolg van die absolute volume van beskikbare informasie. Die tweede probleem spruit voort uit die feit dat ten spyte van die beskikbare informasie, lei organisasies steeds aan 'n gebrek aan algehele informasie, organisasies kan dus nooit toegang he tot al die informasie wat benodig word om die impak te verminder van die onsekerheid wat so kenmerkend is van die wereld ekonomie. Organisasies loop dus altyd die gevaar om irrelevant te raak as hulle nie konstant aanpas by nuwe omstandighede nie. Hierdie soeke na konstante verandering en die afhanklikheid op informasie het verskeie organisasie teoretici en ekonome daartoe gelei om 'n vergelyking te tref tussen die wereld ekonomie en organisasies aan die een kant en nie-Iiniere sisteme wat in die natuur voorkom. Voorbeelde van sulke sisteme sluit lewende organismes, ekostelsels en sterre stelsels in. Die komponente van al hierdie sisteme is op 'n komplekse wyse inmekaar geweef en interafhanklik op mekaar binne die raamwerk van gemeenskaplike omgewing waarvoor hierdie komponente mede verantwoordelik is. Nie-liniere sisteme is van besondere belang vir organisasie teoretici omdat die betrokke sisteme informasie verwerk aangaande hul omgewing om op 'n onvoorspelbare wyse aan te pas by onvoorspelbare veranderinge in die omgewing. Sulke sisteme is uitsonderlik standvastig deurdat hulle kan leer en aanpas by verskillende omstandighede. Nog 'n merkbare aspek van sulke sisteme is die duidelik gestruktureerde en komplekse organisasie wat bestaan ten spyte van 'n algehele gebrek aan gesentraliseerde beheer meganismes. Elke komponent is vry om met 'n nuwe ontwerp te eksperimenteer en vanuit die sukses van die komponente spruit die sukses van die sisteem. Die organisasie wat sigbaar is in nie-liniere sisteme staan bekend as self-organisasie omdat dit nie voortspruit uit 'n sentrale beheer meganisme nie maar instede spontaan onstaan as 'n gevolg van die aksies van komponente. Nie-Iiniere sisteme het die potensiaal om meer te kan wees as die somtotaal van hul komponente. Die beginsel van nie-liniere sisteme en selforganisasie het skrywers soos Stacey, Wheatley en Senge daartoe gelei om nuwe idees te ontwikkel rakende organisasie ontwikkeling, leierskap en strategiese beplanning in organisasies. Hierdie idees is gegrond in wat algemeen bekend staan as 'The New Science'. Die idees van hierdie skrywers is gemik daarop om organisasies aan te moedig om raak te sien dat die wereld ekonomie soos 'n nie-liniere sisteem funksioneer en dat organisasies as sulks 'n beter kans staan om sukses te behaal as hulle sou leer om die beginsels van nie-liniere sisteme te begryp en die inherente kreatiewe en organiserings eienskappe van sulke sisteme uit te buit.

Nous entendons confronter pratique des mathématiques et réflexions sur les mathématiques dans l'œuvre de Weyl. Nous étudierons : (a) ses monographies en analyse complexe, en relativité générale et en mécanique quantique, (b) les articles en lien avec ces ouvrages, (c) certains de ses cours, (d) sa correspondance avec divers scientifiques, principalement A. Einstein, E. Cartan, J. von Neumann. Nous voulons savoir si les théories mathématiques qu'il investit conditionnent ses positions sur les fondements des mathématiques. Inversement, nous montrerons que les philosophies auxquelles il se réfère – essentiellement le criticisme kantien, l'idéalisme fichtéen et la phénoménologie de Husserl – conditionnent ses recherches. Tout d'abord, nous reviendrons sur Die Idee der Riemannschen Fläche (première éd. 1913). Nous montrerons qu'il opte alors pour un formalisme mitigé. Il se revendique de deux traditions incarnées par Klein et par Hilbert. Ensuite, nous étudierons les éditions successives de Raum, Zeit, Materie (1918-1923). Nous aborderons le projet d'une géométrie purement infinitésimale qui permet à Weyl de proposer une théorie unifiée des champs, cette dernière étant réfutée par Einstein, Pauli, Reichenbach, Hilbert and Eddington. Nous décrirons aussi la construction et la résolution de son « problème de l'espace » (1921-1923). Nous indiquerons comment la référence aux philosophies de Fichte et de Husserl permet d'éclairer ces deux projets. Enfin, nous commenterons l'article de Weyl sur les groupes de Lie (1925-1926) ainsi que son ouvrage Gruppentheorie und Quantenmechanik (1928, 1931). Son article sur les groupes de Lie manifeste la voie moyenne entre formalisme et intuitionnisme qu'il adopte en 1924. Son ouvrage en mécanique quantique incarne quant à lui un « tournant empirique » dans son épistémologie qu'il conviendra de comparer \`a l'« empirisme logique »
Our purpose consists in comparing Weyl's mathematical practice with his philosophical reflections on mathematics. We will study (a) his monographs on complex analysis, general relativity and quantum mechanics, (b) the articles which are linked to these books, (c) some of his lecture courses, (d) his correspondence with different scientists, mainly A. Einstein, E. Cartan, J. von Neumann. We will show that his mathematical research has a strong influence on the different stands he successively takes regarding the foundations of mathematics. Conversely, we will show that the philosophical systems he refers to (mainly kantian criticism, fichtean idealism and husserlian phenomenology) have a real impact on his investigations in mathematics. We will first analyse Die Idee der Riemannschen Fläche (first edition 1913). In this book, Weyl seems to take up a formalist point of view, but this is partly true. In fact, he is influenced by two traditions respectively embodied by Hilbert and Klein. Then, we will study the successive editions of Raum, Zeit, Materie (1918-1923). We will describe Weyl's project of a “purely infinitesimal geometry”. Thanks to this geometrical framework, he builds a unified fields theory, which will be disproved by Einstein, Pauli, Reichenbach, Hilbert and Eddington. During this short period, Weyl also constructs and solves the so-called space problem (1921-1923). Weyl's references to Fichte and Husserl have a significant impact on these two projects. Finally, we will comment Weyl's main article on Lie groups (1925-1926) and his monograph on quantum mechanics, i.e. Gruppentheorie und Quantenmechanik (1rst ed. 1928, 2nd ed. 1931). Weyl's article on Lie groups is in accordance with his compromise between intuitionism and formalism (1924). On the other hand, Weyl's book on quantum mechanics encapsulates an “empirical turn” in his epistemology, which will be compared with the so-called empirical logicism

Thesis (Ph.D.)--State University of New York at Buffalo, 2006.
Title from PDF title page (viewed on Mar. 08, 2007) Available through UMI ProQuest Digital Dissertations. Thesis adviser: Sussman, Henry. Includes bibliographical references.

Axiomatic quantum field theory is one approach to the project of merging the special theory of relativity with that of ordinary quantum mechanics. The project begins with the postulation of a set of axioms. Axioms should be motivated by reasonable physical principles in a way that illustrates how a given axiom is true. Motivations are often grounded in the principles of the parent theories: ordinary quantum mechanics or the theory of special relativity. Amongst the set of axioms first proposed by Haag and Kastler in 1963 is the axiom of microcausality. Microcausality requires the observables of regions at space-like separation to commute. This thesis seeks to answer the question ‘What principles from the special theory of relativity or ordinary quantum mechanics motivate, or justify, accepting microcausality as an axiom?’ The first chapter will provide the necessary background to investigate this question and the second chapter will undertake that investigation. In conclusion, microcausality cannot be well-motivated by individual principles rooted in the special theory of relativity or ordinary quantum mechanics.

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.

This dissertation gives a general account of the properties of unitarily inequivalent representations (UIRs) in both canonical quantum field theory and algebraic quantum field theory. A simple model is constructed and then used to show how to build a broad spectrum of UIRs including a version of Haag’s theorem. Haag and Kastler,P, two of the founding fathers of algebraic quantum field theory, argue that the problems posed by UIRs are solved by adopting a notion of equivalence that is weaker than unitary equivalence, which they refer to as physical equivalence. In the dissertation, it is shown that their notion does not provide a suitable classificatory schema. Some of the most important physical representations fail to satisfy the mathematical conditions of their notion. However, Haag and Kastler's notion has an unexpected connection with classical observables. A theorem is proven in which two representations make the same predictions with respect to all classical observables if and only if they satisfy their notion of physical equivalence. Following Haag and Kastler's lead, it was claimed by most proponents of algebraic quantum field theory that all physical content resides in a specific class of observables. It is shown in the dissertation that such claims are exaggerated and misleading. UIRs are used to elucidate the nature of quantum field theory by showing that UIRs have different expectation values for some classical observables of the system, such as temperature and chemical potential, which are not in Haag and Kastler’s specific class. It is shown how UIRs may be used to construct classical observables. To capture the physical content of quantum field theory it is shown that a much larger algebra than that of Haag and Kastler is necessary. Finally, the arguments that UIRs are incommensurable theories are shown to be flawed. The lesson of UIRs is that the mathematical structures in both canonical quantum field theory and Haag and Kastler’s version of algebraic quantum field theory are not sufficient to capture all of the physical content that UIRs represent. A suitable algebraic structure for quantum field theory is provided in the dissertation.
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Philosophers traditionally engage with metaphysical questions at the frontiers of physics by treating theories as putatively fundamental and complete. While this interpretative strategy sits uneasily with the limited success of past theories, it breaks down with the failure of our best current theories, Quantum Field Theories (QFTs), to consistently describe the world on the smallest scales. My dissertation examines how physicists' reconceptualization of successful theories as effective theories affects the epistemological and semantic foundations of the interpretative practice in physics. Chapter 1 offers a detailed analysis of renormalization theory, the set of methods that underwrite physicists' construction of empirically successful QFTs. Chapter 2 demonstrates that effective theories are not merely the only candidates left for scientific realists in QFT but also worth interpreting in realist terms. Chapter 3 shows that effective theories stand as a challenge for traditional approaches to scientific representation and realism in physics. I suggest that indexing truth to physical scales is the most promising way to account for the success of effective theories in realist terms. Chapter 4 develops the referential component of this proposal by taking a detour through the problem of referential failure across theory-change. I argue that to reliably assess referential success before theory-change, we need to index reference-fixing to the limited physical contexts where a given theory is empirically reliable.

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This paper examines how such fundamental notions as causality and determinism have undergone changes as a direct result of empirical discoveries. Although such notions are often regarded as metaphysical or a priori concepts, experimental discoveries at the beginning of this century¿radioactive decay, blackbody radiation and spontaneous emission-led to a direct questioning of the notions of causality and determinism. Experimental evidence suggests that these two notions must be separated. Causality and indeterminism are compatible with the behavior of quantum-mechanical systems. The argument also sheds some light on the Duhem-Quine thesis, since experimental results at the periphery of the conceptual scheme directly affect conceptions at the very core.

Dans cette thèse l’ancienne question philosophique “tout événement a-t-il une cause ?” sera examinée à la lumière de la mécanique quantique et de la théorie des probabilités. Aussi bien en physique qu’en philosophie des sciences la position orthodoxe maintient que le monde physique est indéterministe. Au niveau fondamental de la réalité physique – au niveau quantique – les événements se passeraient sans causes, mais par chance, par hasard ‘irréductible’. Le théorème physique le plus précis qui mène à cette conclusion est le théorème de Bell. Ici les prémisses de ce théorème seront réexaminées. Il sera rappelé que d’autres solutions au théorème que l’indéterminisme sont envisageables, dont certaines sont connues mais négligées, comme le ‘superdéterminisme’. Mais il sera argué que d’autres solutions compatibles avec le déterminisme existent, notamment en étudiant des systèmes physiques modèles. Une des conclusions générales de cette thèse est que l’interprétation du théorème de Bell et de la mécanique quantique dépend crucialement des prémisses philosophiques desquelles on part. Par exemple, au sein de la vision d’un Spinoza, le monde quantique peut bien être compris comme étant déterministe. Mais il est argué qu’aussi un déterminisme nettement moins radical que celui de Spinoza n’est pas éliminé par les expériences physiques. Si cela est vrai, le débat ‘déterminisme – indéterminisme’ n’est pas décidé au laboratoire : il reste philosophique et ouvert – contrairement à ce que l’on pense souvent. Dans la deuxième partie de cette thèse un modèle pour l’interprétation de la probabilité sera proposé. Une étude conceptuelle de la notion de probabilité indique que l’hypothèse du déterminisme aide à mieux comprendre ce que c’est qu’un ‘système probabiliste’. Il semble que le déterminisme peut répondre à certaines questions pour lesquelles l’indéterminisme n’a pas de réponses. Pour cette raison nous conclurons que la conjecture de Laplace – à savoir que la théorie des probabilités présuppose une réalité déterministe sous-jacente – garde toute sa légitimité. Dans cette thèse aussi bien les méthodes de la philosophie que de la physique seront utilisées. Il apparaît que les deux domaines sont ici solidement reliés, et qu’ils offrent un vaste potentiel de fertilisation croisée – donc bidirectionnelle.
In this thesis the ancient philosophical question whether ‘everything has a cause’ will be examined in the light of quantum mechanics and probability theory. In the physics and philosophy of science communities the orthodox position states that the physical world is indeterministic. On the deepest level of physical reality – the quantum level – things or events would have no causes but happen by chance, by irreducible hazard. Arguably the clearest and most convincing theorem that led to this conclusion is Bell’s theorem. Here the premises of this theorem will be re-evaluated, notably by investigating physical model systems. It will be recalled that other solutions to the theorem than indeterminism exist, some of which are known but neglected, such as ‘superdeterminism’. But it will be argued that also other solutions compatible with determinism exist. One general conclusion will be that the interpretation of Bell’s theorem and quantum mechanics hinges on the philosophical premises from which one starts. For instance, within a worldview à la Spinoza the quantum world may well be seen as deterministic. But it is argued that also much ‘softer’ determinism than Spinoza’s is not excluded by the existing experiments. If that is true the ‘determinism – indeterminism’ is not decided in the laboratory: it remains philosophical and open-ended – contrary to what is often believed. In the second part of the thesis a model for the interpretation of probability will be proposed. A conceptual study of the notion of probability indicates that the hypothesis of determinism is instrumental for understanding what ‘probabilistic systems’ are. It seems that determinism answers certain questions that cannot be answered by indeterminism. Therefore we believe there is room for the conjecture that probability theory cannot not do without a deterministic reality underneath probability – as Laplace claimed. Throughout the thesis the methods of philosophy and physics will be used. Both fields appear to be solidly intertwined here, and to offer a large potential for cross-fertilization – in both directions.

My dissertation is situated at the intersection of modernism, print culture, and early-twentieth-century post-Newtonian physics, namely relativity theory and quantum theory. I investigate the ways in which the emerging concept of the unknowable—loosely defined as that which is beyond knowledge but maintains an influence on what can be known—catalyzed a cultural reorientation away from Victorian notions of positivism and progress and toward those aspects of reality that resist knowledge. Although a great deal of critical attention has been paid to modernism’s epistemological uniqueness, scholars are only beginning to acknowledge that concurrent revolutions in physics both reflected and influenced modernists’ conceptions of history, subjectivity, and aesthetics. Scholars such as Gillian Beer, Michael Whitworth, and Mark S. Morrisson have demonstrated that print and popular culture provided crucial avenues through which scientific ideas were disseminated in British society. Furthermore, their research has shown that modernist authors not only read popular science material but also published their work alongside articles about science in a variety of magazines, journals, and newspapers. Building on these connections, I show that books and periodicals served as platforms for dialogue and ideological exchange between science and literature as both disciplines increasingly recognized and grappled with the pervasive influence of the unknowable.

The dissertation brings together approaches across the fields of physics, critical theory, literary studies, philosophy of physics, sociology of science, and history of science to synthesize a hybrid approach for instigating more rigorous and intense cross-disciplinary interrogations between the sciences and the humanities. I explore the concept of speculation in particle physics and science fiction to examine emergent critical approaches for working in the two areas of literature and physics (the latter through critical science studies), but with the expectation of contributing new insights to media theory, critical code studies, and also the science studies of science fiction.

There are two levels of conversations going on in the dissertation; at the first level, the discussion is centered on a critical historiography and philosophical implications of the discovery Higgs boson in relation to its position at the intersection of old (current) and the potential for new possibilities in quantum physics; I then position my findings on the Higgs boson in connection to the double-slit experiment that represents foundational inquiries into quantum physics, to demonstrate the bridge between fundamental physics and high energy particle physics. The conceptualization of the variants of the double-slit experiment informs the aforementioned critical comparisons. At the second level of the conversation, theories are produced from a close study of the physics objects as speculative engine for new knowledge generation that are then reconceptualized and re-articulated for extrapolation into the speculative ontology of hard science fiction, particularly the hard science fiction written with the double intent of speaking to the science while producing imaginative and socially conscious science through the literary affordances of science fiction. The works of science fiction examined here demonstrate the tension between the internal values of physics in the practice of theory and experiment and questions on ethics, culture, and morality.

Nevertheless, the dissertation hopes to show the beginnings of a possibility, through the contentious but generative space provided by speculative physics, to produce more cross-collaborative thinking between physics as represented by the hard sciences, and science fiction representing the objects of literary enterprise and creative evolution.

Dissertation