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AGPhil: Arbeitsgruppe Philosophie der Physik

AGPhil 5: Rods, Clocks, Space and Energy in General Relativity

AGPhil 5.3: Vortrag

Mittwoch, 18. März 2015, 16:15–16:45, A 060

Gravitational energy in general relativity — •James Read — Merton College, University of Oxford, OX1 4JD, UK

Recently, various authors have argued both for and against the proposition that the gravitational field described in General Relativity (GR) possesses ``genuine'' energy. I approach this debate systematically, by (1) presenting the various energy-momentum conservation laws in the theory (both local and global on the one hand, and for either matter energy or matter-plus-gravitational energy via a stress-energy pseudotensor on the other); (2) providing general philosophical principles according to which one can isolate the fundamental form that conservation laws in GR should take (contra much of the literature, this form is not that of an integral conservation law); and (3) using these criteria to identify the energy-momentum conservation laws in GR of greatest significance, and in turn to establish whether gravitational energy really does exist in GR. On (3), I find that, following conservative functionalist principles, genuine gravitational energy does exist in GR, but only in a restricted sense, when certain physical conditions apply. In addition, I argue that one can be a realist about gravitational energy even if one is a relationist about spacetime ontology, as adopting the latter position does not alter the fact that GR contains well-defined quantities which play the functional role of gravitational energy.