20 May: Patricia Palacios on Equilibrium in Long-Range Interacting Systems

Our spring FraMEPhys Seminar series continued with a talk from Dr Patricia Palacios (University of Salzburg) on Monday 20th May 2019.

Violent relaxation (!) is the phenomenon of faster-than-expected approach to equilibrium for systems like galaxies with long-range gravitational interactions

Patricia’s title was “Re-defining equilibrium for long-range interacting systems” (joint work with Lapo Casetti, University of Florence). The abstract is as follows:

“Long-range interacting systems (LRI) are systems in which the interaction potential decays slowly for large inter-particle distance. Typical examples of long-range interactions are the gravitational and Coulomb forces. The philosophical interest for studying these kinds of systems has to do with the fact that they exhibit properties that escape traditional definitions of equilibrium based on stationary probability distributions. How should we define equilibrium for LRI then? In this contribution, we argue that a comparison with ergodicity-breaking phase transitions gives us a qualitative understanding of equilibrium for these kinds of systems in terms of metastable equilibria. As in the case of phase transitions, we contend that in LRI one could account for metastable equilibria by defining the dynamics for finite-time scales. However, in contrast to phase transitions, we show that these metastable states depend on unknown initial conditions and do not correspond to Boltzmannian equilibrium. This negative conclusion provides a possible basis for future scientific research.” 

There was a reading group with the speaker from 1.30-2.30pm before the talk, also in ERI 149. We discussed “Mind the Gap: Boltzmannian versus Gibbsian Equilibrium” by Charlotte Werndl and Roman Frigg.

Katie Robertson at DIEP, Amsterdam: “Emergence and Reduction: Go Hand in Hand?”

On 10 May 2019 Katie Robertson was in Amsterdam to give a paper on the relation between reduction and emergence at the workshop ‘Emergence: conceptual and philosophical aspects’ organized by the Dutch Institute for Emergent Phenomena.

diep

Katie’s main conclusion: The irreversible equations of SM can be reduced to the underlying microdynamics — but the resultant time-asymmetry is emergent. A reduced theory will often describe emergent entities that are novel (if the reduction is ‘vertical’) and robust (if the reduction/construction will reveal which lower-level differences did not matter).

Oxford Philosophy of Physics Events – Summer 2019

Followers of FraMEPhys might be interested in the following talks at the University of Oxford during May and June 2019:

Thursday May 2: Olivier Darrigol (Paris)
Philosophy of Physics Seminar (Lecture Room, Radcliffe Humanities), 4.30 p.m.

Ludwig Boltzmann: Atoms, mechanics, and probability
Statistical mechanics owes much more to Ludwig Boltzmann than is usually believed. In his attempts to derived thermodynamic and transport phenomena from deeper microphysical assumptions, he explored at least five different approaches: One based on mechanical analogies (with periodic mechanical systems or with statistical ensembles), one based on Maxwell’s collision formula, one based on the ergodic hypothesis, one based on combinatorial probabilities, and one based on the existence of thermodynamic equilibrium. I will sketch this various approaches and show how Boltzmann judged them and interconnected them. It will also argue that in general Boltzmann was more concerned with constructive efficiency than with precise conceptual foundations. Basic questions on the reality of atoms or on the nature of probabilities played only a secondary role in his theoretical enterprise.

Friday May 3: Nancy Cartwright (Durham and UC San Diego),
Jowett Society (Lecture Room, Radcliffe Humanities), 3.30 p.m.

‘Nature the artful modeler’
Are our hugely effective scientific laws – like equations we use in physics for precise prediction and technology – true? No. But they are not false either. They are not proper propositions in competition for truth or falsehood. What we find in physics texts and articles are not well-formed formulae but equations and ‘principles’ without, e.g., quantifiers and ‘ceteris paribus’ conditions included. Nor, I shall argue, can they be turned into proper propositions and still do all the jobs we require of them. They are rather materials we have learned how to use to build models and claims that are not only candidates for truth but, in any common sense of the word, are true. We are artful modelers, and we have insufficient reason to think it could ever be different. I urge that, as good empiricists should, we take successful scientific practice as our guide to what the world is like. Our best bet then about Nature is that she is not in the business of following out some laws writ in heavenly books any more than we are. She too is an artful modeler. The talk will defend the claim that we recoup the facts by artful modelling and explain what it means to claim that that is what Nature does too.

Thursday May 16: Jeremy Butterfield (Cambridge)
Philosophy of Physics Seminar (Lecture Room, Radcliffe Humanities), 4.30 p.m.

On realism and functionalism about space and time
(Joint work with Henrique Gomes.) In this talk I will set the recent literature on spacetime functionalism in context, by discussing two traditions that form its background. First: functionalism in general, as a species of inter-theoretic reduction. Second: relationism about space and time.

Thursday May 30: Henrique Gomes (Perimeter and Cambridge)
Philosophy of Physics Seminar (Lecture Room, Radcliffe Humanities), 4.30 p.m.

Gauge, boundaries, and the connection form
Forces such as electromagnetism and gravity reach across the Universe; they are the long-ranged forces in current physics. And yet, in many applications—theoretical and otherwise—we only have access to finite domains of the world. For instance, in computations of entanglement entropy, e.g. for black holes or cosmic horizons, we raise boundaries to separate the known from the unknown. In this talk, I will argue we do not understand gauge theory as well as we think we do, when boundaries are present. For example: It is agreed by all that we should aim to construct variables that have a one to one relationship to the theory’s physical content within bounded regions. But puzzles arise if we try to combine definitions of strictly physical variables in different parts of the world.

Thursday June 6: Martin Lesourd (Oxford)
Philosophy of Physics Seminar (Lecture Room, Radcliffe Humanities), 4.30 p.m.

Reasoning on the basis of past lightcones
We shall ask the following: in general relativistic spacetimes, what can observers know about their spacetime on the basis of their past lightcones? After briefly describing the inductive character of this question, I will review and describe the significance of various known results, due in particular to Malament 1977 and Manchak 2009. I will then present some new ones and explain how they bear on the former. Time permitting, I shall briefly describe the idea behind general relativity’s foremost open problem – the conjecture of strong cosmic censorship – along with its potential relevance. 

Thursday June 13: Harvey Brown (Oxford)
Philosophy of Physics Seminar (Lecture Room, Radcliffe Humanities), 4.30 p.m.

Title and abstract TBA.

Thursday June 20: John Bush (MIT),
Mathematical Institute (Woodstock Rd, OX26GG), 5.00 p.m.

Walking on water: from biolocomotion to quantum foundations
In this lecture John Bush will present seemingly disparate research topics which are in fact united by a common theme and underlaid by a common mathematical framework.  First there is the ingenuity of the natural world where living creatures use surface tension to support themselves on the water surface and propel themselves along it. Then there is a system discovered by Yves Couder only fifteen years ago, in which a small droplet bounces along the surface of a vibrating liquid bath, guided or ‘piloted’ by its own wave field. Its ability to reproduce many features previously thought to be exclusive to quantum systems has launched the field of hydrodynamic quantum analogs, and motivated a critical revisitation of the philosophical foundations of quantum mechanics.

Please email external-relations@maths.ox.ac.uk to register.
This talk will be streamed live on:
https://facebook.com/OxfordMathematics
https://livestream.com/oxuni/bush

3 April: Levels of Explanation Workshop – Schedule now available

How do explanations within physics relate to explanations in other sciences, and what different levels of explanation can be distinguished within physics itself? To help answer these questions, on Monday 3rd April FraMEPhys hosted a workshop at the University of Birmingham on Levels of Explanation, with talks from Karen Crowther, Alex Franklin, Lina Jansson, Eleanor Knox, Christian List and David Yates.

A schedule and abstracts are now available at the workshop page.

Al Wilson in Stockholm: “Emergent Contingency”

On 14 March 2019 Al Wilson was at the Department of Philosophy at the University of Stockholm to give a talk titled ‘Emergent Contingency’ – on the general prospects of naturalistic metaphysics, on how to bring science to bear on modality, and on how Everettian quantum theory can underwrite a naturalistic theory of contingency. Fun was had (we think) by all. Abstract and slides are below!

Abstract: I develop and defend a reductive account of objective contingency in nature, drawing on resources from Everettian (many-worlds) quantum mechanics. I distinguish four degrees of naturalistic involvement in the theory of modality; the proposed quantum modal realism is naturalistic in all four senses. I also sketch some consequences of the account for the methodology of metaphysics.

11 March: Laura Felline, “The Measurement Problem in Quantum Information Theory”

Our next visitor in the FraMEPhys Seminar series was Dr Laura Felline (Roma Tre) who spoke on Monday 11th March. Laura’s title was ‘The Measurement Problem in Quantum Information Theory’ and her abstract was as follows:

“In this talk I criticize the idea, wide-spread between the advocates of Quantum Information Theory, that in order to explain away the measurement problem it is sufficient to reject the assumption that the quantum state represents physical objects. In order to do that, I will analyse three notable information-theoretic approaches to QT: Bub’s new information-theoretic interpretation (as a representative of a psi-ontic approach), Pitowsky’s Bayesian interpretation (as a representative of an objective psi-epistemic approach) and Qbism (as a representative of a subjective psi-epistemic approach) and argue that the measurement problem still affects the first two interpretations, while Qbism leads to an unacceptable clash between the alleged content of quantum theory and scientific practice.”

Laura argued that the Wigner’s friend thought-experiment, for different reasons in each case, undermines all of the main information-theoretic ‘solutions’ to the measurement problem.

Before the talk, there was a reading group with the speaker in ERI G54 from 1.30-2.30pm. The paper discussed was “An Introduction to QBism with an Application to the Locality of Quantum Mechanics” by Fuchs, Mermin and Schack, available here: https://arxiv.org/pdf/1311.5253.pdf

25 Feb: Antonio Vassallo, “Dependence Relations in General Relativity”

The second talk in our spring FraMEPhys Seminar series was given by Dr Antonio Vassallo (University of Barcelona) on Monday 25th February 2019. Antonio’s title was “Dependence Relations in General Relativity”, and his abstract was as follows:

“I will discuss the nature of the dependence relations underpinning the talk of mutual action between material and spatiotemporal structures in general relativity. In particular, I will present a case study involving frame-dragging effects. Frame-dragging relates local inertial frames to distant distributions of matter in a time-independent way, thus establishing some sort of non-local link between the two. For this reason, a plain causal interpretation of frame-dragging faces huge challenges. By using a generalized structural equation model analysis I will argue that frame-dragging is best understood in terms of a novel type of dependence relation that is half-way between causation and grounding.”

Antonio’s central argument was that the lawlike status of the Einstein Equations renders the overall frame-dragging model explanation as partly causal and partly metaphysical.

There was a reading group before the talk, outside in the February sunshine, where we read Carl Hoefer’s “Mach’s Principle as Action-at-a-distance in General Relativity: The Causality Question”.