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Empirical Equivalence, Artificial Gauge Freedom and a Generalized Kretschmann Objection

Pitts, J. Brian (2009) Empirical Equivalence, Artificial Gauge Freedom and a Generalized Kretschmann Objection. [Preprint]

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    Abstract

    Einstein considered general covariance to characterize the novelty of his General Theory of Relativity (GTR), but Kretschmann thought it merely a formal feature that any theory could have. The claim that GTR is ``already parametrized'' suggests analyzing substantive general covariance as formal general covariance achieved without hiding preferred coordinates as scalar ``clock fields,'' much as Einstein construed general covariance as the lack of preferred coordinates. Physicists often install gauge symmetries artificially with additional fields, as in the transition from Proca's to Stueckelberg's electromagnetism. Some post-positivist philosophers, due to realist sympathies, are committed to judging Stueckelberg's electromagnetism distinct from and inferior to Proca's. By contrast, physicists identify them, the differences being gauge-dependent and hence unreal. It is often useful to install gauge freedom in theories with broken gauge symmetries (second-class constraints) using a modified Batalin-Fradkin-Tyutin (BFT) procedure. Massive GTR, for which parametrization and a Lagrangian BFT-like procedure appear to coincide, mimics GTR's general covariance apart from telltale clock fields. A generalized procedure for installing artificial gauge freedom subsumes parametrization and BFT, while being more Lagrangian-friendly than BFT, leaving any primary constraints unchanged and using a non-BFT boundary condition. Artificial gauge freedom licenses a generalized Kretschmann objection. However, features of paradigm cases of artificial gauge freedom might help to demonstrate a principled distinction between substantive and merely formal gauge symmetry.


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    Item Type: Preprint
    Keywords: general covariance, gauge freedom, clock fields, constrained dynamics, theory equivalence, Kretschmann objection
    Subjects: Specific Sciences > Physics > Symmetries/Invariances
    Specific Sciences > Physics > Relativity Theory
    Specific Sciences > Physics > Fields and Particles
    General Issues > Logical Positivism/Logical Empiricism
    Depositing User: Dr. Dr. J. Brian Pitts
    Date Deposited: 24 Nov 2009
    Last Modified: 07 Oct 2010 11:18
    Item ID: 4995
    URI: http://philsci-archive.pitt.edu/id/eprint/4995

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