Computability and physical theories / R. Geroch and J.B. Hartle -- Excess baggage -- Sources of predictability -- The no-boundary wave function of the universe -- Scientific knowledge from the perspective of quantum cosmology -- The physics of 'now' -- The quantum mechanics of closed systems -- The spacetime approach to quantum mechanics -- Quantum physics and human language -- Quantum pasts and the utility of history -- The quasiclassical realms of this quantum universe -- Living in a superposition -- The quantum mechanical arrows of time -- Why our universe is comprehensible -- Quantum cosmology : problems for the 21st century -- Anthropic reasoning and quantum cosmology -- Are we typical? / J.B. Hartle and M. Srednicki -- Science in a very large universe / M. Srednicki and J.B. Hartle -- The observer strikes back / J.B. Hartle and T. Hertog -- Quantum multiverses -- Quantum mechanics at the Planck scale -- The state of the universe -- The impact of cosmology on quantum mechanics -- Murray Gell-Mann : a short appreciation -- Working with Stephen Hawking
Computability and physical theories / R. Geroch and J.B. Hartle -- Excess baggage -- Sources of predictability -- The no-boundary wave function of the universe -- Scientific knowledge from the perspective of quantum cosmology -- The physics of 'now' -- The quantum mechanics of closed systems -- The spacetime approach to quantum mechanics -- Quantum physics and human language -- Quantum pasts and the utility of history -- The quasiclassical realms of this quantum universe -- Living in a superposition -- The quantum mechanical arrows of time -- Why our universe is comprehensible -- Quantum cosmology : problems for the 21st century -- Anthropic reasoning and quantum cosmology -- Are we typical? / J.B. Hartle and M. Srednicki -- Science in a very large universe / M. Srednicki and J.B. Hartle -- The observer strikes back / J.B. Hartle and T. Hertog -- Quantum multiverses -- Quantum mechanics at the Planck scale -- The state of the universe -- The impact of cosmology on quantum mechanics -- Murray Gell-Mann : a short appreciation -- Working with Stephen Hawking
QUANTUM COSMOLOGY It is an honor, of course, but also a pleasure for me to join in this celebration of Murray Gell-Mann's sixtieth birthday and to address such a distinguished audience. Murray was my teacher and more recently we have worked together in the search for a quantum framework within which to erect a fundamental description of the universe which would encompass all scales – from the microscopic scales of the elementary particle interactions to the most distant reaches of the realm of the galaxies – from the moment of the big bang to the most distant future that one can contemplate. Such a framework is needed if we accept, as we have every reason to, that at a basic level the laws of physics are quantum mechanical. Further, as I shall argue below, there are important features of our observations which require such a framework for their explanation. This application of quantum physics to the universe as a whole has come to be called the subject of quantum cosmology. The assignment of the organizers was to speak on the topic “Where are our efforts leading?” I took this as an invitation to speculate, for I think that it is characteristic of the frontier areas of science that, while we may know what direction we are headed, we seldom know where we will wind up.
Preface. In defense of dogma: why there cannot be a relativistic quantum mechanics of (localizable) particles D.B. Malament. Just how radical is hyperplane dependence? G. Fleming. Is there superluminal causation in relativistic quantum field theory? M. Redei. EPR, relativity, and the GHZ experiment C. Pagonis, et al. Hidden quantum non-locality N.D. Mermin. Royer's measurements - the rise and fall of (yet another) signalling scheme I. Pitowsky. Tails of Schrodinger's cat D.Z. Albert, B. Loewer. Wavefunction collapse models with nonwhite noise P. Pearle. The emergence of classical properties from quantum mechanics L.E. Ballentine. Relativism S. Saunders. Wave and particle concepts in quantum field theory P. Teller. The conceptual relation between standard quantum mechanics and quantum field theory D. Robinson. What measurement problem? J.T. Cushing. Bovine metaphysics: remarks on the significance of the gravitational phase effect in quantum mechanics H.R. Brown. Exotic (quixotic?) applications of Bohm theory R. Weingard. Complementarity and the orthodox (Dirac-von Neumann) interpretation of quantum mechanics J. Bub. Logical reflections on the Kochen-Specker theorem J.L. Bell. Construction of quantum mechanics via commutative operations S. Kochen.
The universe we live in is both strange and interesting. This strangeness comes about because, at the most fundamental level, the universe is governed by the laws of quantum mechanics. This is the most spectacularly accurate and powerful theory ever devised, one that has given us insights into many aspects of the world, from the structure of matter to the meaning of information. This textbook provides a comprehensive account of all things quantum. It starts by introducing the wavefunction and its interpretation as an ephemeral wave of complex probability, before delving into the mathematical formalism of quantum mechanics and exploring its diverse applications, from atomic physics and scattering, to quantum computing. Designed to be accessible, this volume is suitable for both students and researchers, beginning with the basics before progressing to more advanced topics.
We consider Gell-Mann and Hartle's consistent histories formulation of quantum cosmology in the interpretation in which one history, chosen randomly according to the decoherence functional probabilities, is realized from each consistent set. We show that in this interpretation, if one assumes that an observed quasiclassical structure will continue to be quasiclassical, one cannot infer that it will obey the predictions of classical or Copenhagen quantum mechanics. \textcopyright{} 1996 The American Physical Society.
Quantum physics is believed to be the fundamental theory underlying our understanding of the physical universe. However, it is based on concepts and principles that have always been difficult to understand and controversial in their interpretation. This book aims to explain these issues using a minimum of technical language and mathematics. After a brief introduction to the ideas of quantum physics, the problems of interpretation are identified and explained. The rest of the book surveys, describes and criticises a range of suggestions that have been made with the aim of resolving these problems; these include the traditional, or 'Copenhagen' interpretation, the possible role of the conscious mind in measurement and the postulate of parallel universes. This new edition has been revised throughout to take into account developments in this field over the past fifteen years, including the idea of 'consistent histories' to which a completely new chapter is devoted.
It will be presented in this chapter a historical account of the consistent histories interpretation of quantum mechanics based on primary and secondary literature. Firstly, the formalism of the consistent histories approach will be outlined. Secondly, the works by Robert Griffiths and Roland Omnès will be discussed. Griffiths' seminal 1984 paper, the first physicist to have proposed a consistent-histories interpretation of quantum mechanics, followed by Omnès' 1990 paper, were instrumental to the consistent-histories model based on Boolean logic. Thirdly, Murray Gell-Mann and James Hartle's steps to their own version of consistent-histories approach, motivated by a cosmological perspective, will then be described and evaluated. Gell-Mann and Hartle understood that spontaneous decoherence could path the way to a concrete physical model to Griffiths' consistent histories. Moreover, the collective biography of these figures will be put in the context of the role played by the Santa Fe Institute, co-founded by Gell-Mann in 1984 in Santa Fe, New Mexico, where Hartle is also a member of the external faculty.