All meetings for TT25 will be held on Thursdays at 13:00 - see below for details of location for each week.​​​​

​​

Week 4 (22/5): Lem Tsikas (Bristol) - The Coarse-Grained Gibbs Entropy and the Phase-averaged Boltzmann Entropy

Location: Ryle Room, Radcliffe Humanities Building

​

Abstract: I will discuss the relation between two important quantities in statistical mechanics: the coarse-grained Gibbs entropy and the phase-averaged Boltzmann entropy. These quantities (I will argue) are the best options for reducing thermodynamic entropy available to the Gibbsian and Boltzmannian frameworks respectively. Gibbsians must use the coarse-grained Gibbs entropy since the fine-grain version is a constant of motion, and makes the use of probability distributions hard to justify. Boltzmannians meanwhile ought to use the phase-averaged Boltzmann entropy, since this gives them access to probability distributions, which are an indispensable tool. They also ought not to have a problem with using these distributions, since Boltzmannian qualms with probability distributions fall flat if we are not committed to using the Gibbs entropy to reduce thermodynamic entropy.

 

The coarse-grained Gibbs entropy and the phase-averaged Boltzmann entropy are related simply - the difference between them is equal to the Shannon entropy of the distribution over macro-states (i.e. the probabilities in the entropy function are probabilities of being in a certain macro-state, not in a certain micro-state). This means that disagreements between the two is much easier to quantify than in the case of the un-averaged Boltzmann entropy and the fine-grain Gibbs entropy; that debate usually requires argumentation around the concept of equilibrium, and the status of probabilities. Specifically, it means that the two frameworks agree to the extent that the distribution used is certain about the macro-state of the system. I will explore this consequence for a variety of ways we could interpret and set the probability function, namely, as a credence function, as the actual distribution of many systems, as the actual state of a single system, and as the distribution of a single system over a period of time.

​

Week 5 (29/5): Bryan Cheng (Oxford) - Title TBC

Location: Seminar Room, Radcliffe Humanities Building

​

Week 6 (5/6): Felix Muller (Oxford) - Title TBC

Location: Littlegate Room, Pembroke College

​

Week 7 (12/6): Dominic Ryder (LSE) - Title TBC

Location: Ryle Room, Radcliffe Humanities Building

​

Week 8 (19/6): Eleanor March (Oxford) - Minimal coupling, the strong equivalence principle, and the adaptation of matter to spacetime geometry

Location: Littlegate Room, Pembroke College

​

Abstract: I provide a systematic exploration of one set of precise technical conditions under which matter fields might be said to be "adapted" to a relativistic spacetime geometry - namely, that the equations governing those matter fields be minimally coupled, quasilinear, and symmetric hyperbolic. In particular, I show that this class of theories necessarily satisfy (i) the dominant energy condition, (ii) the conservation condition, and (iii) the Geroch-Earman causality condition. (This suffices for them to satisfy a version of the geodesic principle, and closes the gap between Geroch-Earman causality and the dominant energy condition.) I also discuss the relationships between minimal coupling, the "strong equivalence principle", "local (approximate) Poincaré symmetry", and the "local validity of special relativity", thus clearing up issues in the geometry-dynamics debate about the meaning and status of those principles.

​​​​​​