Topology of pulsating active matter: Defect asymmetry controls emergent motility

Luca Casagrande; Alessandro Manacorda; Étienne Fodor

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arXiv · 2605.25996

Topology of pulsating active matter: Defect asymmetry controls emergent motility

Luca Casagrande·Alessandro Manacorda·Étienne Fodor

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Abstract

In pulsating active matter, topological defects are motile despite the absence of any macroscopic flows and microscopic self-propulsion. We reveal that this motility arises from a ratchet effect: the mechanochemical coupling between local oscillations and repulsive interactions breaks both spatial and time-reversal symmetries, thus leading asymmetric rotating defects to drift under fluctuations. This mechanism regulates a crossover between spiral waves connecting slow defects and fiber-like waves connecting fast defects, in analogy with the onset of heart rhythm disorder in cardiac tissues. We rationalize this crossover in terms of a fluctuating hydrodynamics that captures how motile defects spontaneously nucleate and move within an ordered background.

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Luca Casagrande, Alessandro Manacorda, Étienne Fodor. 2026-05-25. Topology of pulsating active matter: Defect asymmetry controls emergent motility. https://arxiv.org/abs/2605.25996

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