10 - Conclusion
Published online by Cambridge University Press: 06 July 2010
Summary
In this book I have tried to present a compact and unified perspective on quantum gravity, its technical aspects and its conceptual problems, the way I understand them. There are a great number of other aspects of quantum gravity that I would have wished to cover, but my energies are limited. Just to mention a few of the major topics I have left out: 2 + 1 gravity, the Kodama state and related results, quantum gravity phenomenology, supergravity in LQG, coherent states … Here I briefly summarize the physical picture that emerges from LQG and the solution it proposes to the characteristic conceptual issues of quantum gravity. I conclude with a short summary of the main open problems and the main results of the theory.
The physical picture of loop gravity
The effort to develop a quantum theory of gravity forces us to revise some conventional physical ideas. This was expected, given the conceptual novelty of the two ingredients, GR and QM, and the tension between the two. The physical picture presented in this book has emerged from several decades of research, and is a tentative solution of the puzzle. Here is a brief summary of its conceptual consequences.
GR and QM
The first conclusion of loop gravity is that GR and QM do not contradict each other. A quantum theory that has GR as its classical limit appears to exist. In order to merge, both QM and classical GR have to be suitably formulated and interpreted. More precisely, they both modify some aspects of classical prerelativistic physics, and therefore some aspects of each other.
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- Quantum Gravity , pp. 366 - 374Publisher: Cambridge University PressPrint publication year: 2004