Earman, John (2022) Trace-Free Gravitational Theory (aka Unimodular Gravity) for Philosophers. [Preprint]
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Abstract
Trace-free gravitational theory (also known as unimodular gravity) has been touted as a means to resolving the cosmological constant problem, widely regarded as one of the most important unsolved problems of fundamental physics. The claim that the resolution takes the form of decoupling vacuum energy from the dynamics of the spacetime metric is critically examined and found wanting. The weaker claim that the theory ameliorates the fine tuning version of the cosmological constant problem is more plausible but still disputable. Unimodular gravity is observationally equivalent to standard general relativity theory at the classical level, but this observational equivalence may be broken at the quantum level, at least if some branches of the canonical quantization road to quantum gravity are followed. Unimodular gravity thus offers a quick access to foundations issues in classical and quantum gravity, as well as insights into the considerations that motivate contemporary gravitational research. As such, it deserves more attention than it has received from the philosophy of physics community. The purpose of this paper is to lay out the issues surrounding unimodular gravity in a manner that will be an invitation to more philosophical scrutiny.
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Item Type: | Preprint | ||||||
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Keywords: | general relativity theory; unimodular gravity; quantum gravity; cosmological constant | ||||||
Subjects: | Specific Sciences > Physics > Cosmology Specific Sciences > Physics > Fields and Particles General Issues > Laws of Nature Specific Sciences > Physics > Quantum Gravity General Issues > Realism/Anti-realism Specific Sciences > Physics > Relativity Theory General Issues > Structure of Theories |
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Depositing User: | John Earman | ||||||
Date Deposited: | 18 Jun 2022 14:49 | ||||||
Last Modified: | 18 Jun 2022 14:49 | ||||||
Item ID: | 20765 | ||||||
Subjects: | Specific Sciences > Physics > Cosmology Specific Sciences > Physics > Fields and Particles General Issues > Laws of Nature Specific Sciences > Physics > Quantum Gravity General Issues > Realism/Anti-realism Specific Sciences > Physics > Relativity Theory General Issues > Structure of Theories |
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Date: | 17 June 2022 | ||||||
URI: | https://philsci-archive.pitt.edu/id/eprint/20765 |
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