CANCELLED - SoftBio Theory Seminar

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)