Two Challenges to the Requirement of Substantive General Covariance |
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Authors: | J Earman |
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Institution: | (1) Department of History and Philosophy and Science, University of Pittsburgh, 1017 Cathedral of Learning, Pittsburgh, PA, 15217, U.S.A. |
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Abstract: | It is generally acknowledged that the requirement that the laws of a spacetime theory be covariant under a general coordinate
transformation is a restriction on the form but not the content of the theory. The prevalent view in the physics community
holds that the substantive version of general covariance – exhibited, for example, by Einstein’s general theory of relativity
– consists in the requirement that diffeomorphism invariance is a gauge symmetry of the theory. This conception of general
covariance is explained and confronted by two challenges. One challenge claims, in effect, that substantive general covariance
is not deserving of the name since, just as it is possible to rewrite any spacetime so that it satisfies formal general covariance,
so it is also possible to rewrite the theory so that it satisfies the proffered version of substantive general covariance.
The other challenge claims that the proffered version of substantive general covariance is not strong enough to guarantee
the intended meaning of general covariance. Both challenges are discussed in terms of concrete examples. It is argued that
both challenges fail but, at the same time, that they help to clarify what is at stake on the seemingly never ending dispute
over the nature and status of general covariance. |
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Keywords: | |
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