10 June: Dan Marshall on Facts and Grounding

A supplementary FraMEPhys Seminar was given by project visitor Dan Marshall (Lingnan University) on Monday 10th June 2019.

Dan’s title was “Facts and Grounding”.

Abstract: The most popular theories of the individuation conditions of facts are the coarse-grain theory, according to which facts are identical if and only if they are necessarily equivalent, and the structure theory, according to which facts are structured in the same kind of way sentences are structured. Despite their popularity, both these theories have serious problems. In this paper, I propose a new moderate-grain theory of facts that avoids these problems by individuating states of affairs more finely than the coarse-grain theory and more coarsely than the structure theory. I then defend the proposed theory from the objection that it is incompatible with widely accepted principles of grounding by arguing that these principles of grounding are false and should be replaced with alternative principles.

3 June: Mark Pexton on Contextuality, Emergence and Unification

The next in our series of FraMEPhys Seminars was given by Mark Pexton (Durham) on Monday 3rd June 2019.

Mark’s title was “Contextuality, Emergence and Unification in Physics”.

Abstract: A contextual account of emergence and unification is presented. It is argued that emergent phenomena can be thought of as the consequence of system/context interactions. Contexts often involve modal relations not contained in the first order level of the system in question, hence although the system itself may appear reducible, the combination of system and context is not. Unification as an explanatory strategy can sometimes be seen as linked with reductionist intuitions – by considering their reduction base, disparate systems can be shown to be different manifestations of the same underlying phenomena. However, unifications do not proceed via reduction bases alone. Sometimes they involve moving up a ‘level’ of modal space to unify disparate microphysical phenomena by considering unifying features of the properties of aggregates (such as in universality in critical phenomena). It is argued that unification itself as an explanatory strategy (and therefore putative guide to ontological commitments) is itself highly contextual. Unifications can proceed by shifting the demarcations between systems and contexts to provide new system/context boundaries that create different sets of ‘similar’ unified physical phenomena. As such unification does not easily fit a standard paradigm of reduction or emergence.

There was a reading group with the speaker before the talk. We discussed “Reduction and emergence in the fractional quantum Hall state”, joint work between Tom Lancaster and Mark.

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).

25 June: Matt Farr, “Do we need to explain initial conditions?”

Our final visitor in the 2019 FraMEPhys Spring Seminar series will be Dr Matt Farr (Cambridge), who will speak at 3pm on Tuesday 25 June 2019, room TBC. Matt’s title and abstract will be as follows: 

Do we need to explain initial conditions?
It is common to think of the universe as a grand time-directed process that started out in some initial state — call this the ‘time-directed universe’ hypothesis (TDU). On TDU, the initial state is explanatorily unique — it is the only one that did not evolve from some prior set of conditions. Some have appealed to this explanatory uniqueness to suggest that it is misguided to seek an explanation as to why the early universe was extremely low-entropy, and so argue that TDU plays an important explanatory role in physics. But what if we reject TDU? This talk considers the options for those that assume a temporally adirectional metaphysics, which I call the ‘C theory’. Given the C theory holds there is no intrinsic difference between ‘initial’ and ‘final’ states of physical systems, it is unclear what we are to make of the explanatory demands of the low entropy early universe. I assess a series of options for the C theory, arguing that the rejection of TDU leaves us no worse off with regard to explaining the low entropy early universe.

Before the talk, there will be a reading group with the speaker at 1.30pm in ERI 159. The paper we’ll discuss is “Measures, Explanations and the Past: Should ‘Special’ Initial Conditions be Explained?” by Craig Callender, available here: https://doi.org/10.1093/bjps/55.2.195