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DTSTART;TZID=Europe/London:20201019T140000
DTEND;TZID=Europe/London:20201019T153000
DTSTAMP:20211016T211136
CREATED:20201006T150247Z
LAST-MODIFIED:20201015T115150Z
UID:15271-1603116000-1603121400@www.lse.ac.uk
SUMMARY:Henrique Gomes & Jeremy Butterfield (Cambridge): "Geometrodynamics as Functionalism about Time"
DESCRIPTION:This event will take place online via Zoom. \nEveryone is welcome to join using a computer with access to the internet and Zoom. To take part just follow these instructions: \n\nDownload Zoom\nJoin the event using this link: https://lse.zoom.us/j/89944283581\n\nPlease note that these events are routinely recorded\, with the edited footage being made publicly available on our website and YouTube channel. We will only record the audio\, the slides and the speaker and will not include the Q&A section. However\, any question asked during the talk itself will feature in the final edit. \n\nAbstract: A recent literature about a doctrine called ‘spacetime functionalism’ focuses on how the physics of matter and radiation contributes to determining\, or perhaps even determines or explains\, chrono-geometry. Thus spacetime functionalism is closely related to relational\, and specifically\nMachian\, approaches to chrono-geometry and dynamics; and to what has recently been called the ‘dynamical approach’ to chrono-geometry. \nWe are sympathetic to spacetime functionalism. We have elsewhere argued that in its best form\, it says that a chrono-geometric concept (or concepts) is uniquely definable in terms of (and so reducible to) matter and radiation – and then proves a theorem to this effect. We also gave examples of such theorems from the older literature in foundations of chrono-geometry (before the recent label ‘functionalism’). \nThis paper argues that three projects in the physics literature give vivid and impressive illustrations of this kind of functionalist reduction\, for time. That is: they each provide\, within a theory about spatial geometry\, a functionalist reduction of the temporal metric and time-evolution. And\nthe reduction is summed up in a theorem that the temporal metric and-or the Hamiltonian governing time-evolution is\, in an appropriate sense\, unique. \nThese three projects are all ‘general-relativistic’. But they differ substantially in exactly what they assume\, and in what they deduce. They are\, in short: \n(1): The recovery of geometrodynamics\, i.e. general relativity’s usual Hamiltonian\, from requirements on deformations of hypersurfaces in a Lorentzian spacetime. This is due to Hojman et al. (1976). \n(2): The programme of Schuller\, Duell et al. (2011\, 2012\, 2018). They deduce from assumptions about matter and radiation in a 4-dimensional manifold that is not initially assumed to have a Lorentzian metric\, the existence of a generalized metric (in some cases a Lorentzian one) – and much information about how it relates to matter and radiation. \n(3): The deduction of general relativity’s usual Hamiltonian in a framework without even a spacetime: that is\, without initially assuming a 4-dimensional manifold\, let alone one with a Lorentzian metric. This is due to Gomes and Shyam (2017). \nWe discuss these projects in order. We end by drawing a positive corollary of (3)\, for a recent programme in the foundations of classical gravity\, viz. shape dynamics. \n
URL:https://www.lse.ac.uk/philosophy/events/gomes-butterfield-geometrodynamics-as-functionalism-about-time/
CATEGORIES:Sigma Club
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