Dear all:Philosophers of physics will be interested to read details below of upcoming LSE Sigma Club talks occasional Mondays at 14.00, on Zoom; 19 October, 30 Nov, and 7 December.
Also: on Tuesdays at 14.00 to 15.30, on Zoom, there is a Cambridge course, taught by Bryan Roberts and Jeremy Butterfiled, on Philosophy of quantum field theory (continues in Lent 2021);
for course descriptions, reading list, and later, handouts: go to: http://personal.lse.ac.uk/robert49/teaching/partiii/ Best, Jeremy and Bryan ------ Jeremy Butterfield: Trinity College, Cambridge CB2 1TQ: Tel: 07557-668413 (mobile) ---------- Forwarded message ---------- Date: Wed, 7 Oct 2020 13:14:27 +0000 From: "[utf-8] LSE Sigma Club" <[email protected]> To: "[utf-8] Jeremy" <[email protected]> Subject: [utf-8] The Sigma Club is back! Upcoming online philosophy of physics talks from LSE View this email in your browser (https://mailchi.mp/14b5c64e3697/upcoming-sigma-club-lectures-5163617?e=99c5d1f64f) https://lse.us10.list-manage.com/track/click?u=166f0feae024825349b394635&id=b45cbd5020&e=99c5d1f64f Dear Philosophers of Physics, The LSE Sigma Club is back! This term's programme features talks by Henrique Gomes & Jeremy Butterfield, Chrysovalantis Stergiou and Neil Dewar, further info below. Of course, as with so many things, this term will be a little different from previous years, with all of our talks now taking place online via Zoom. The information for joining will be added to each event page at least a week in advance. We'll also send this information out by email for each of the talks. So keep an eye out for further emails and we hope to see many of you at our first talk on 19 October! Best wishes, Centre for Philosophy of Natural and Social Science 19 October, 2pm ** Henrique Gomes & Jeremy Butterfield (Cambridge): âGeometrodynamics as Functionalism about Timeâ (https://lse.us10.list-manage.com/track/click?u=166f0feae024825349b394635&id=30dde66a75&e=99c5d1f64f) ------------------------------------------------------------ A recent literature about a doctrine called âspacetime functionalismâ 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 Machian, approaches to chrono-geometry and dynamics; and to what has recently been called the âdynamical approachâ to chrono-geometry. We 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 â 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 âfunctionalismâ). This 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 the reduction is summed up in a theorem that the temporal metric and-or the Hamiltonian governing time-evolution is, in an appropriate sense, unique. These three projects are all âgeneral-relativisticâ. But they differ substantially in exactly what they assume, and in what they deduce. They are, in short: (1): The recovery of geometrodynamics, i.e. general relativityâs usual Hamiltonian, from requirements on deformations of hypersurfaces in a Lorentzian spacetime. This is due to Hojman et al. (1976). (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) â and much information about how it relates to matter and radiation. (3): The deduction of general relativityâs 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). We 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. ------------------------------------------------------------ 30 November, 2pm ** Chrysovalantis Stergiou (The American College of Greece): âOn Empirical Underdetermination of Physical Theories in C*Algebraic Settingâ (https://lse.us10.list-manage.com/track/click?u=166f0feae024825349b394635&id=55e2596c97&e=99c5d1f64f) ------------------------------------------------------------ Empirical underdetermination of physical theories by observational data lies at the heart of the debate over scientific realism. Antirealists of different strands contend that if observation cannot determine the state of a physical system then to talk about a uniquely defined state of the system is just a matter of convention. In the context of Algebraic Quantum Field Theory (AQFT) this stance is related to the claim that the physical topology of the state space is the weak*-topology and to what has become known as Algebraic Imperialism, the operationalist attitude which characterized the first steps of the theory. Aristidis Arageorgis (1995) devised a mathematical argument against empirical underdetermination of the state of a system in C*-algebraic setting which rests on two topological properties of the state space: being T1 and being first countable in the weak*-topology. The first property is possessed trivially by the state space while the latter is highly non-trivial and it can be derived from the assumption that the algebra of observables is separable. In this talk we will reconstruct Arageorgisâ argument and examine its soundness with regard to the separability of the algebra of observables. We will show that separability is related to two factors: (a) the dimension of the algebra, considered as a vector space; (b) whether it is a C*- or von Neumann algebra. Finite-dimensional C*-algebras and von Neumann algebras are separable, infinite-dimensional von Neumann algebras are non-separable and infinite-dimensional C*-algebras can be separable. These considerations will be discussed with reference to classical systems of N particles, the Heisenberg model for ferromagnetism, the Haag-Araki formulation of AQFT and a separable reformulation of AQFT in Minkowski spacetime suggested by Porrmann (1999, 2004). This talk is dedicated to the memory of my beloved teacher, colleague and friend Aris Arageorgis who untimely passed away in 2018. ------------------------------------------------------------ 7 December, 2pm ** Neil Dewar (Munich): âOn Absolute Unitsâ (https://lse.us10.list-manage.com/track/click?u=166f0feae024825349b394635&id=8bd5ba2b97&e=99c5d1f64f) ------------------------------------------------------------ What is the best way to characterise the intrinsic structure of physical quantities? Fieldâs program shows one approach (that also delivers a nominalist treatment of such quantities); in this talk, I outline how group-theoretic methods can deliver a somewhat simpler, although non-nominalist, way of doing this for scalar and vector quantities. I go on to develop a theory on how such quantities can be algebraically combined, and use this to develop a simple intrinsic treatment of Newtonian gravitation. Finally, I argue that this treatment illuminates a âthird wayâ in the debate over absolutism and comparativism about quantities: namely, a form of anti-quidditist absolutism. https://lse.us10.list-manage.com/track/click?u=166f0feae024825349b394635&id=9dda9e4a0e&e=99c5d1f64f https://lse.us10.list-manage.com/track/click?u=166f0feae024825349b394635&id=a141930c88&e=99c5d1f64f https://lse.us10.list-manage.com/track/click?u=166f0feae024825349b394635&id=b30df548a5&e=99c5d1f64f https://lse.us10.list-manage.com/track/click?u=166f0feae024825349b394635&id=6173f2cd9d&e=99c5d1f64f ============================================================ Copyright © 2020 LSE Philosophy, Logic and Scientific Method, All rights reserved. You are receiving this email because you signed up for the LSE Sigma Club mailing list. 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