arXiv subjects

Emma Lång

Publications and source records attributed to Emma Lång.

2 recordsLinked to original sources

arXiv2026

Memory-driven topological ordering during the transition from dormant to migrating epithelia

Transitions from quiescence to collective migration in epithelia underlie wound healing and cancer invasion, yet their physical origin remains poorly understood. Here we show that quiescent epithelial monolayers store spatially contractile stresses that function as a form of mechanical memory. Upon serum-induced reactivation, these pre-stressed regions nucleate extensile asters that emit propagating polarity domain walls. Along these interfaces, topological defects are created, advected and annihilated, leading to defect coarsening with faster kinetics than by elastic interactions. An active elastic model quantitatively reproduces the observed dynamics and identifies stored stress as the origin of rapid topological reorganization. Our results establish a mechanism in which mechanical memory in quiescent epithelia triggers active stress release, driving collective migration via rapid topological ordering, distinct from conventional unjamming and flocking transitions.

cond-mat.soft↗

arXiv2025

Topological defects in polar active matter

Polar active matter - including animal herds, aggregates of motile cells and active colloids - often forms coordinated migration patterns, such as flocking. This orderly motion can be disrupted by full-integer topological defects representing localized disturbances where polar alignment is lost. Such polar defects can serve as key organizing centers across scales, sustaining collective behavior, such as swirling motion and other large-scale coherent states. While significant progress in understanding active matter principles have been made in recent years, a quantitative understanding of how topological defects influence active polar matter is needed. We present a brief overview of recent experimental observations in synthetic active colloids and various biological systems. We describe how polar defects mediate dynamical transitions and contribute to the spontaneous emergence of large-scale coherent states. We also discuss theoretical advancements in physical modeling of coupled processes involving polar defects and collective behavior in active polar matter.

cond-mat.soft↗