Sarah Loos
Credit: Stefan Münster

CANCELLED - SoftBio Theory Seminar

03 Jun 2024
Seminars and colloquia
Simpkins Lee
Beecroft Building

Sarah Loos (University of Cambridge)

Knowledge of physics?
Yes, knowledge of physics required
For more information contact


Reciprocity is a hallmark of thermal equilibrium, but ubiquitously broken in nonequilibrium systems. I will give some insights into how nonreciprocal interactions can fundamentally affect the phases and fluctuations of many-body systems. 
First, in binary fluids, nonreciprocal coupling between fluid components can cause the emergence of travelling waves through PT symmetry-breaking phase transitions. Using a nonreciprocal field model, we show that at such transitions fluctuations not only inflate, as in equilibrium criticality, but also develop an asymptotically increasing time-reversal asymmetry [1-3]. The formation of dissipative patterns and the emergence of irreversible fluctuations can both be attributed to a mechanism of mode coupling in the vicinity of critical exception points. For a nonreciprocal Cahn-Hilliard model, we show that this manifests itself in "self-propelled" interfaces whose dynamics can be mapped to the motion of a single microswimmer [3]. Second, introducing nonreciprocal coupling in the two-dimensional XY model, we show how nonreciprocity can lead to the formation of true long-range order [4], as well as dynamical phases, glassy behaviour, and chaos.

[1] Suchanek, Kroy & Loos: Irreversible mesoscale fluctuations herald the emergence of dynamical phases, PRL 131, 258302 (2023)
[2] Suchanek, Kroy & Loos: Time-reversal and parity-time symmetry breaking in non-Hermitian field theories, PRE 108, 064123 (2023)
[3] Suchanek, Kroy & Loos: Entropy production in the nonreciprocal Cahn-Hilliard model, PRE 108, 064610 (2023)
[4] Loos, Klapp & Martynec: Long-Range Order and Directional Defect Propagation in the Nonreciprocal XY Model with Vision Cone Interactions, PRL 130, 198301 (2023)