Sarah Loos
Postdoctoral Researcher at the Department of Applied Mathematics and Theoretical Physics, Corpus Christi College, University of Cambridge, UK
https://www.corpus.cam.ac.uk/people/dr-sarah-loos
Phase transitions and Fluctuations of systems with nonreciprocal interactions
Reciprocity is a hallmark of thermal equilibrium, but ubiquitously broken in far-from-equilibrium systems. I will give some insights into how nonreciprocal interactions can fundamentally affect the phases and fluctuations of many-body systems. Using a two-dimensional XY model, where spins interact only with neighbours within their ‘vision cones’, we show how nonreciprocity can lead to true long-range order and directional propagation of defects [1]. In binary fluids, nonreciprocal coupling between fluid components can cause the emergence of travelling waves through PT symmetry-breaking phase transitions. Using a hydrodynamic model, we find that fluctuations not only inflate, as in equilibrium criticality, but also develop an asymptotically increasing time-reversal asymmetry [2-4] and associated surging entropy production. We can trace the formation of dissipative patterns and the emergence of irreversible fluctuations to the same origin, namely a mode-coupling mechanism near critical exceptional points.
[1] Loos, Klapp, Martynec, Long-Range Order and Directional Defect Propagation in the Nonreciprocal XY Model with Vision Cone Interactions, Phys. Rev. Lett. 130, 198301 (2023).
[2] Suchanek, Kroy, Loos, Irreversible mesoscale fluctuations herald the emergence of dynamical phases, Phys. Rev. Lett. in press (2023).
[3] Suchanek, Kroy, Loos, Time-reversal and parity-time symmetry breaking in non-Hermitian field theories, Phys. Rev. E in press (2023).
[4] Suchanek, Kroy, Loos, Entropy production in the nonreciprocal Cahn-Hilliard model, Phys. Rev. E in press (2023).