New preprint!
So, say you're studying some critical transition. How do you catch its universality? Pair correlations? Boring!
We threw line segments at the system, looked at intersections with clusters, and uncovered static and dynamical universal behavior of MIPS!
arxiv.org/abs/2511.09444
Alt: a close up of a person's hand holding a marker that says sharpie
This was a blast from the past since the early version of the dynamical action part was derived during COVID, then dropped as I really needed some fresh (and ventilated) air. Shoutout @satyamanand.bsky.social for giving me the motivation to actually make this work public during our recent collab!
And as a byproduct, we also predict the behavior of a single particle in a thermostat-tachostat, showing that polarity dynamics display non-trivial dynamics. In particular, polarities develop an effective mobility that could have been naïvely confused for an active-like effective temperature.
We then write the dynamical action and study time-reversal properties. We recover the standard fluctuation-dissipation theorem in the co-moving frame... but for an extended time-reversal operation that also flips the polarity of particles, as if they were magnetic moments.
M. Kasiulis
M. Kasiulis
M. Kasiulis
This has concrete consequences: the response of the system violates the standard Onsager reciprocity, replaced by Onsager-Casimir like in charged particles in magnetic fields. Also, if you just look at the system naïvely with the usual time-reversal operation, it looks like it's non-equilibrium!
It is an honor and a pleasure to be spontaneously featured in Optica's official outreach platform!
Many inspiring papers published in Optica's journals were read in the making of this work, so it feels like a nice loop 😄
www.optica-opn.org/home/newsroo...
M. Kasiulis
M. Kasiulis
A cool collaboration with István Kovács's group at Northwestern, that brings ideas from conformal field theory and quantum spin chains all the way to active matter!
Poke @nyuphysics.bsky.social
ALT: a close up of a blue background with a swirl of water .
The model has an "extended" Gibbs measure ft. both energy and momentum due to its non-Galilean nature. Thus, proper Langevin dynamics should have a bath that not only plays the role of a thermostat, enforcing temperature, but also of a tachostat, enforcing velocity, like a crowd walking around you!
Today on arxiv, a blast from the past: Hamiltonian flocks! Some years ago we showed that this conservative model could support collective motion. In this preprint, I discuss how to properly couple the model to a bath and the effects of time-reversal symmetry in it! arxiv.org/abs/2604.02914
M. Kasiulis
ALT: a cartoon clock with arms and a bow tie shows the time as almost 5:00
The fluctuation-dissipation theorem is a hallmark of equilibrium system that stem from their time-reversal symmetry. In many non-equilibrium systems, in particular active ones, extensions and explicit...
