Berlin 2015 – scientific programme

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AGPhil: Arbeitsgruppe Philosophie der Physik

AGPhil 4: Foundations of Classical Gravity

AGPhil 4.2: Talk

Wednesday, March 18, 2015, 10:15–10:45, A 060

Einstein's Physical Strategy, Energy Conservation, Symmetries and Stability — •J. Brian Pitts — University of Cambridge

Work by Renn, Janssen et al. shows that Einstein found his field equations partly by a physical strategy including the Newtonian limit, the electromagnetic analogy, and energy conservation. What energy-momentum complex(es) did he use and why? Given that Lagrange and Jacobi linked symmetries and conservation, did Einstein tie conservation to symmetries, and if so, to which? How did the work relate to emerging knowledge (1911-14) of the canonical energy-momentum tensor and its translation-induced conservation in Herglotz, Mie and Born? After initially using energy-momentum tensors hand-crafted from the gravitational field equations, Einstein used an identity from his assumed linear coordinate covariance x^m'= A^m_n x^n to relate it to the canonical tensor. Whereas Mie and Born were concerned about the canonical tensor's asymmetry, Einstein did not need to worry because his Entwurf Lagrangian is modelled not so much on Maxwell's theory (which avoids negative-energies) as on a scalar theory (the Newtonian limit) with symmetric canonical tensor. The Entwurf theory has 3 negative-energy field degrees of freedom. Thus it fails a 1920s-30s priori particle physics test with roots in Lagrange's stability theorem---c.f. Einstein's 1915 Entwurf critique for not admitting rotating coordinates and not getting Mercury's perihelion right.

This work is partly collaborative with Alex Blum.