Realism and Intertheory Relationships: Interstructuralism, Closed Theories and the Quantum-Classical Limit
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Realism and Intertheory Relationships: Interstructuralism, Closed Theories and the Quantum-Classical Limit Nahuel Sznajderhaus Submitted in accordance with the requirements for the degree of Doctor of Philosophy The University of Leeds School of Philosophy, Religion, and History of Science December 2016 The candidate confirms that the work submitted is his own and that appropriate credit has been given where reference has been made to the work of others. This copy has been supplied on the understanding that it is copyright material and that no quotation from the thesis may be published without proper acknowledgement c 2016 The University of Leeds and Nahuel Sznajderhaus The right of Nahuel Sznajderhaus to be identified as Author of this work has been asserted by him in accordance with the Copyright, Designs and Patents Act 1988. Acknowledgements The biggest thank you to mi mam´ay mi pap´a,for your support, encouragement and for giving me Argentina. It has been an honour to have Steven French as my supervisor. I've learned so much from him about philosophy, physics and academia. His feedback, guidance, optimism and encouragement have been crucial. It has been an honour to have Juha Saatsi and Alisa Bokulich as my examiners. I thank them for their inspiring papers, meaningful and critical questions, comments and discussions. I have thought and learned most about my views by discussing with others, particularly in pubs, but also in seminars and conferences. I acknowledge the conversations, heated discussions and long emails with: Alberto Cordero, Anna Marmodoro, Carl Warom, Chris Timpson, David Wallace, Davide Romano, Fabio Ceravolo, Federico Holik, Gra- ciela Domenech, Guido Bacciagaluppi, Jade Fletcher, Jakob Sprickerhof, James Fraser, John Delos, John Pemberton, Jorge Orozco, Juan Campos Quemada, Klaas Landsman, Matthias Egg, Mengli Du, Nahuel Freitas, Nick Tasker, Pablo Poggi, Paul Knott, Simon Newey, Spencer Hey, V´ıctorDur`a-Vil`a,Wim Christiaens, Samuel Schindler. To Christian de Ronde, from whom I learned so much over these years in physics and philosophy, for his inspiring work and for being always there when I needed advice and discussions, cosmic kite. To Liz Watkins, Dani Adams, Sarah Adams, Will Gamester and Nick Tasker for editorial comments. Especially to the Darwin Trust of Edinburgh for the PhD scholarship. Above all, to Louise ML, for the inspiration, for her patience (a lot of that), for her support and immense optimism. For being the best company ever. For her love. iii Abstract Today there is no agreement on which, if any, of the several known realist interpreta- tions of quantum mechanics is the correct one, and disagreement on this matter is not merely verbal, but substantial. However, I will show that the interpretations share a common aim: to recover the classical world given that it is quantum. This aim responds to implicit and well-entrenched philosophical intuitions that can be phrased in terms of intertheory relations, traditionally involving theory reduction, in philosophy, and the quantum-classical limit, in the foundations of physics. However, not one of those notions is free from controversies, and many contest that there is a smooth transition from the quantum to the classical. Hence, the account of the relationship between quantum mech- anics and classical mechanics is an unresolved problem, and the philosophical character of the underlying framework can be contested. This thesis will offer a critical analysis of current well-known realist interpretations and will also put forward an alternative framework. I will critically examine traditional views on intertheory relations and the recent view of interstructuralism. My main claim will be that the role of intertheory relations is overrated, because a more basic question has to be answered first: `what is a quantum system?'. That will motivate my novel view. I will critically evaluate and defend an alternative view based on the philosophy of Werner Heisenberg. The view proposes that physical theories should be regarded as \closed" systems. This has immediate implications for how we should understand intertheory relations in general, as well as scientific realism in particular. My view will appear radical in comparison to traditional views of quantum mechanics. Yet, I will examine fruitful comparison with forms of realism such as perspectivism and metaphysical pluralism. I shall conclude with indications for future work. iv Contents Declaration of Authorship ii Acknowledgements iii Abstract iv Table of Contentsv Abbreviations ix 1 Introduction1 2 The Received View of the Realist Interpretation of QM9 2.1 Introduction...................................9 2.2 Realist Interpretations of QM and the Received View............ 15 2.2.1 The Measurement Problem and the Appearance of Classicalities. 16 2.2.2 Everettian Interpretations....................... 21 2.2.3 Bohmian Mechanics.......................... 23 2.2.4 The Ghirardi-Rimini-Weber Interpretation............. 25 2.2.5 Wavefunction Realism......................... 27 2.2.6 Modal Interpretations......................... 29 2.3 Conclusions................................... 31 3 Intertheory Relations: Theory Reduction and the QM-CM Limit 33 3.1 Intertheory Relations: Useful Distinctions.................. 33 3.2 Theory Reduction............................... 40 3.2.1 Nagelian Reduction.......................... 41 3.2.2 Nickles Reduction2 ........................... 45 3.2.3 Post's Heuristic Correspondence Principle.............. 48 3.2.4 Emergence............................... 54 3.3 The Received Account of the QM-CM Limit and its Problems....... 57 3.3.1 Mathematical Limits.......................... 61 3.3.2 Ehrenfest's Theorem.......................... 65 3.3.3 Moyal Brackets............................. 67 3.3.4 Decoherence and the QM-CM Limit................. 69 3.4 Alternatives to the Received Account of the QM-CM Relation....... 89 v 3.5 Conclusions................................... 93 4 The Interstructuralist Approach (I): Physical Bones 95 4.1 Introduction................................... 95 4.2 Open Theories and the Reciprocal Correspondence Principle Methodology 96 4.3 Semiclassical Mechanics: Quantum Chaos and Mesoscopic Phenomena.. 99 4.3.1 Einstein-Brillouin-Keller Quantisation................ 101 4.3.2 Trace Formula............................. 105 4.4 The General Correspondence Principle: Rydberg Atoms in Strong Mag- netic Fields................................... 109 4.4.1 The Trace Formula and the Rydberg Spectrum........... 116 4.5 The Inverse Correspondence Principle: the Helium Atom......... 120 4.6 A Novel Phenomenon: Wavefunction Scarring................ 122 4.7 On the `Quantum' Nature of Semiclassical Phenomena........... 127 4.8 Conclusions................................... 130 5 The Interstructuralist Approach (II): Philosophical Flesh 133 5.1 Introduction................................... 133 5.2 Scientific Explanation and Interstructuralism................ 134 5.2.1 Hempel's DN Model.......................... 134 5.2.2 Salmon's Causal Explanation..................... 136 5.2.3 Woodward's Causal-Counterfactual Account............. 137 5.2.4 Bokulich's own Model-Structural Explanation............ 139 5.2.5 Bokulich's Account of Mesoscopic Phenomena............ 143 5.3 Scientific Realism and Interstructuralism.................. 147 5.3.1 On the Explanatory Role of Fictions................. 149 5.3.2 On the Fictional Character of the Classical Orbits......... 153 5.3.3 Schindler's Criticism.......................... 155 5.3.4 Woodwardians Return......................... 158 5.3.5 The Heuristic Approach to Interstructuralism............ 160 5.4 Conclusions................................... 163 6 Beyond the Received View of QM (I): Realist Strategies 167 6.1 Introduction................................... 167 6.2 Strategies in Realism: Exemplar vs. Recipe................. 169 6.2.1 Exemplar/Recipe and Intertheory Relations............. 172 6.2.2 Exemplar/Recipe and Metaphysics.................. 176 6.3 Metaphysics in Realism: Deep vs. Shallow.................. 178 6.4 Supplementing Core Realism: Heisenberg's Closed Theories........ 182 6.5 An Exemplar Realist View of QM: Core Realism+Closed Theories.... 188 6.6 Conclusions................................... 192 7 Beyond the Received View of QM (II): Other Realisms 195 7.1 Introduction................................... 195 7.2 The Core Realism+Closed Theories View and Other Realisms....... 196 7.2.1 Realism and Perspectives....................... 196 7.2.1.1 Giere's Scientific Perspectivism............... 197 7.2.1.2 Massimi's Perspectival Realism............... 203 vi 7.2.2 Cartwright's Metaphysical Pluralism................. 207 7.3 Conclusions................................... 212 8 Conclusions and Prospects 215 8.1 Decoherence-Up and Rydberg Atoms-Down: Simplifying Heuristics.... 217 8.2 Resuscitation Strategy: Bringing Modal Interpretations Back to Life... 220 A Quantum Superposition 223 Bibliography 225 vii Abbreviations BM Bohmian mechanics CM Classical mechanics DN Deductive nomological EBK Einstein Brillouin Keller GCP General correspondence principle GRW Ghirardi-Rimini-Weber interpretation MIs Modal interpretations MWI Many worlds interpretation PR Perspectival realism QM Quantum mechanics SP Scientific perspectivism SR Structural realism STR Special theory of relativity WKB Wentzel Kramers Brillouin ix Chapter 1 Introduction This chapter sets out the nature, purpose and motivations of this investigation, and