Physics meets philosophy at the Planck scale
Contemporary Theories in Quantum Gravity
William G. Unruh
Publisher: Cambridge University Press
Print Publication Year: 2001
Online Publication Date:December 2009
Online ISBN:9780511612909
Hardback ISBN:9780521662802
Paperback ISBN:9780521664455
Chapter DOI: http://dx.doi.org/10.1017/CBO9780511612909.008
Subjects: History, Philosophy and Foundations of Physics, Quantum Physics, Quantum Information and Quantum Computation
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It has now been 25 years since Hawking (Hawking 1974, 1975, Bardeen, Carter, and Hawking 1973) first surprised the world of physics with his analysis of quantum fields near black holes. Black holes, as their name implies, were believed to be objects into which things could fall, but out of which nothing could come. They were the epitome of black and dark objects. However, Hawking's analysis predicted that black holes should radiate, the radiation should be continuous and thermal, and the temperature should be inversely proportional to the mass of the black hole. Since black holes can also be said to have an energy proportional to their mass, this result led to opening of a whole new field of black hole thermodynamics.
That black holes could behave like thermodynamic objects had been intimated by results over the the previous five years. Christodolou (1970), Hawking and Ellis (1973, especially Lemma 9.2.2), Misner, Thorne, and Wheeler (1973) and Bekenstein (1973, 1974) had shown that there were certain formal similarities between black holes and thermodynamic objects. In particular, if one assumed positive energy for matter (an uncontested assumption), then – as Hawking most clearly showed – the area of a black hole horizon does not decrease. However, this formal similarity with entropy, which also does not decrease for an isolated system, did not seem to have any real relation with thermodynamics. The entropy of a body does not decrease only if the body is isolated, and not in interaction with any other system.
pp. i-vi
pp. vii-viii
pp. ix-x
pp. 1-30
Part I - Theories of Quantum Gravity and their Philosophical Dimensions: Read PDF
pp. 31-32
2 - Spacetime and the philosophical challenge of quantum gravity: Read PDF
pp. 33-89
3 - Naive quantum gravity: Read PDF
pp. 90-100
4 - Quantum spacetime: What do we know?: Read PDF
pp. 101-122
pp. 123-124
5 - Reflections on the fate of spacetime: Read PDF
pp. 125-137
6 - A philosopher looks at string theory: Read PDF
pp. 138-151
7 - Black holes, dumb holes, and entropy: Read PDF
pp. 152-174
Part III - Topological Quantum Field Theory: Read PDF
pp. 175-176
8 - Higher-dimensional algebra and Planck scale physics: Read PDF
pp. 177-196
Part IV - Quantum Gravity and the Interpretation of General Relativity: Read PDF
pp. 197-198
9 - On general covariance and best matching: Read PDF
pp. 199-212
10 - Pre-Socratic quantum gravity: Read PDF
pp. 213-255
11 - The origin of the spacetime metric: Bell's ‘Lorentzian pedagogy’ and its significance in general relativity: Read PDF
pp. 256-272
Part V - Quantum Gravity and the Interpretation of Quantum Mechanics: Read PDF
pp. 273-274
12 - Quantum spacetime without observers: Ontological clarity and the conceptual foundations of quantum gravity: Read PDF
pp. 275-289
13 - On gravity's role in quantum state reduction: Read PDF
pp. 290-304
14 - Why the quantum must yield to gravity: Read PDF
pp. 305-338
pp. 339-356
Notes on contributors: Read PDF
pp. 357-360
pp. 361-365