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arXiv · 2509.19024

Defect statistics in pulsating active liquids: From contraction waves to aster dynamics

Tirthankar Banerjee·Luca Cocconi·Thibault Desaleux·Jonas Ranft·Étienne Fodor
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Abstract

We propose and study a hydrodynamic theory that captures the emergence of contraction waves in dense active liquids composed of pulsating particles subject to isotropic deformation. The coupling between displacement and deformation regulates the interplay between the flow induced by local isotropic deformation and the resistance to pulsation stemming from steric interaction. We reveal that this interplay leads the emergent contraction waves to spontaneously organize into a packing of pacemakers. The relaxation of these pacemakers is governed by a complex feedback between fast and slow aster defects that form in the profiles of velocity flows and of deformation gradients. By mapping contraction waves into these aster defects, we show that such waves adhere to specific constraints, including topological charge conservation and a master curve in the defect velocity statistics, that help rationalize the mechanisms underlying the relaxational dynamics.

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Tirthankar Banerjee, Luca Cocconi, Thibault Desaleux, Jonas Ranft, Étienne Fodor. 2026-09-15. Defect statistics in pulsating active liquids: From contraction waves to aster dynamics. https://arxiv.org/abs/2509.19024

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