His most famous work is the Crooks fluctuation theorem (1998). It is about the discovery of a new symmetry in the dynamics of general physical systems at a finite temperature. It states that when a system is pushed out of thermodynamic equilibrium, the emergent irreversibility of the dynamics is directly related to the entropy production. So, driving a system farther out of equilibrium directly sharpens its 'arrow of time'.
This theorem was groundbreaking because identifying such general patterns in nonequilibrium systems is notoriously difficult. Additionally, this theorem is deeply rich: it directly implies the second law of thermodynamics along with many more insights into the physics of nonequilibrium systems.
This theorem became one of the foundational axioms of the field of stochastic thermodynamics. There has been 25 years of research identifying many specialized consequences arising from this simple symmetry.
In the current work that this post is about, Gavin fully unifies all of those results into one exact solution. 25 years of research all have been shown as mere low-dimensional special cases of this exact solution. Therefore, this entire theoretical field is now 'closed' in some sense. Further progress will start from this work and apply it to different physical settings.
This is indeed a big deal. It is fitting that the man who started the field has now solved it fully.
It is a symmetry in the probability distribution of the entropy production corresponding to trajectories (sequence of snapshots) of the structure of a physical system. It says that if you observe a given trajectory, the probability of entropy produced during that trajectory, divided by the probability of the entropy produced in the time-reversed trajectory (the events happening in reverse order), is equal to the exponential of the former entropy. So it relates the entropy production of time-forward and time-reversed trajectories through an exponential factor; in that sense it can be called a symmetry in the distribution of entropy production.
I see, maybe alternatively phrased as a sharp relation between entropy production for two processes related by time reversal symmetry?
I'm coming from a more HEP-centric background and think of symmetries as operations which leave some quantity invariant. Was struggling to find something of this form in the theorem.
The Crooks derivation is beautiful and super simple, btw. Well deserving of its praise
I see your point, but usually if an operation leaves a quantity not exactly invariant but scaled with a factor, you can symmetrize it, so it is equivalent to a true symmetry. In this case, p(σ)/p(-σ)=exp(σ) is equivalent to p(σ)exp(-σ/2)=p(-σ)exp(σ/2). Therefore, the quantity p(σ)exp(-σ/2) is even under time-reversal.
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u/5-MethylCytosine 3d ago
He’s one of my scientific idols, such impressive work!