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Trace-Free Gravitational Theory (aka Unimodular Gravity) for Philosophers

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
Creators:
CreatorsEmailORCID
Earman, Johnjearman@pitt.edu
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
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
Date: 17 June 2022
URI: https://philsci-archive-dev.library.pitt.edu/id/eprint/20765

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