8 February 2021

Space Science at Droptower SEMINAR TALK

Location: ZARM Bremen - Online seminar
When: 8.2.2021, 17:00 CET - Online

Speaker: Patrick Dürr (Oxford University)

Title: Revisiting Teleparallel Gravity: Spacetime, Theory Identity, and Conventionalism

Abstract: This talk studies some of the conceptual foundations of Teleparallel Gravity (TPG), a gauge theory of gravity (effectively) empirically equivalent to General Relativity (GR). In contrast to the latter, in TPG, spacetime is prima facie no longer curved, with this curvature representing gravity; rather, in TPG gravity is  formally represented by torsion – a feature salient of non-Riemannian geometries. The paper tackles three main tasks. (1) One is to carefully articulate TPG’s interpretation as a theory about reference frames (tetrads) in a Riemann-Cartan spacetime. These clarifications allow us to apply standard criteria for theory individuation – that is, to assess whether TPG and GR count as distinct theories, or merely notational reformulations of each other. (2) The second task is to critically examine various claims, found in the literature, regarding TPG’s advantages over GR, such as its alleged capacity to dispense with “the“ equivalence principle. Only with respect to gravitational energy and with respect to greater coherence with the rest of physics (qua gauge theory), I submit, does TPG indeed display (some) advantage. (3) Notwithstanding these merits, TPG suffers from a number of drawbacks vis-à-vis GR; the main one is the introduction of problematic, in principle undetectable extra structure, not present in GR. Thereby, TPG flouts a form of the Equivalence Principle (viz. the equivalence of all reference frames, related via a local Lorentz transformation). I conclude by pointing out that the coexistence of GR and TPG as empirically equivalent, yet geometrically incompatible desriptions of gravity constitutes a strong argument in favour of a sophisticated, modern form of conventionalism about geometry.