Many Worlds? Everett, Quantum Theory, & Reality

by Saunders, Simon; Barrett, Jonathan; Kent, Adrian; Wallace, David

• ISBN13: 9780199655502
• ISBN10: 0199655502
• Edition: Reprint
• Format: Paperback
• Copyright: 2012-07-26
• Publisher: Oxford University Press

Summary

What does realism about the quantum state imply? What follows when quantum theory is applied without restriction, if need be, to the whole universe? These are the questions which an illustrious team of philosophers and physicists debate in this volume. All the contributors are agreed on realism, and on the need, or the aspiration, for a theory that unites micro- and macroworlds, at least in principle. But the further claim argued by some is that if you allow the Schrödingerequation unrestricted application, supposing the quantum state to be something physically real, then this universe is one of countlessly many others, constantly branching in time, all of which are real. The result is the many worlds theory, also known as the Everett interpretation of quantum mechanics.The contrary claim sees this picture of many worlds as in no sense inherent in quantum mechanics, even when the latter is allowed unrestricted scope and even given that the quantum state itself is something physically real. For this picture of branching worlds fails to make physical sense, let alone common sense, even on its own terms. The status of these worlds, what they are made of, is never adequately explained. Ordinary ideas about time and identity over time become hopelessly compromised.The concept of probability itself is brought into question. This picture of many branching worlds is inchoate, it is a vision, an error. There are realist alternatives to many worlds, some even that preserve the Schrödinger equation unchanged. Twenty specially written essays, accompanied by commentaries and discussions, examine these claims and counterclaims in depth. They focus first on the question of ontology, the existence of worlds (Part 1 and 2), second on the interpretation of probability (Parts 3 and 4), and third on alternatives or additions to many worlds (Parts 5 and 6). The introduction offers a helpful guide to the arguments for the Everett interpretation, particularly as they have been formulated in the last twodecades.

Author Biography

Simon Saunders is Professor in Philosophy of Physics at the University of Oxford. Jonathan Barrett is Lecturer in Mathematics at Royal Holloway, University of London. Adrian Kent is Reader in Quantum Physics at the University of Cambridge. David Wallace is Tutorial Fellow in Philosophy or Science at Balliol College, Oxford

Table of Contents

Many Worlds? An Introduction	p. 1
Why Many Worlds?
Decoherence and Ontology	p. 53
Quasiclassical Realms	p. 73
Macroscopic Superpositions, Decoherent Histories, and the Emergence of Hydrodynamic Behaviour	p. 99
Problems with Ontology
Can the World be Only Wavefunction?	p. 121
A Metaphysician Looks at the Everett Interpretation	p. 144
Commentary: Reply to Hawthorne: Physics before Metaphysics	p. 154
Transcript: Ontology	p. 161
Probability in the Everett Interpretation
Chance in the Everett Interpretation	p. 181
A Fair Deal for Everettians	p. 206
How to Prove the Born Rule	p. 227
Everett and Evidence	p. 264
Critical Replies
One World Versus Many: The Inadequacy of Everettian Accounts of Evolution, Probability, and Scientific Confirmation	p. 307
Probability in the Everett Picture	p. 355
Decisions, Decisions, Decisions: Can Savage Salvage Everettian Probability?	p. 369
Transcript: Probability	p. 391
Alternatives to Many Worlds
Quantum Jumps, Born's Rule, and Objective Reality	p. 409
Two Dogmas About Quantum Mechanics	p. 433
Rabid Dogma? Comments on Bub and Pitowsky	p. 460
The Principal Principle and Probability in the Many-Worlds Interpretation	p. 467
De Broglie-Bohm Pilot-Wave Theory: Many Worlds in Denial?	p. 476
Reply to Valentini, æDe Broglie-Bohm Pilot-Wave Theory: Many Worlds in Denial?'	p. 510
Not Only Many Worlds
Everett and Wheeler, the Untold Story	p. 521
Apart from Universes	p. 542
Many Worlds in Context	p. 553
Time Symmetry and the Many-Worlds Interpretation	p. 582
Transcript: Not (Only) Many Worlds	p. 597
Index	p. 609
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