Hexatic Order Coupled with Thermal Noise Produces Bubbles in Two-Dimensional Active Matter

Fuente: arXiv
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Main Authors: Langford, Luke, Omar, Ahmad K.
Format: Preprint
Published: 2026
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author Langford, Luke
Omar, Ahmad K.
author_facet Langford, Luke
Omar, Ahmad K.
contents The phase separation of purely-repulsive particles induced by self-propulsion is among the most well-studied non-equilibrium phase transitions. However, some notable features of this transition remain open questions, including the origin of bubbles within the dense phase in two dimensions. Various explanations have been proposed, ranging from a reversal of the Ostwald ripening process to topological defects at the borders of hexatic domains. We present particle-based simulations that disentangle the effect of hexatic domains on the bubble size and number distribution through the introduction of polydispersity. While hexatic order is found to be necessary for bubble formation, we also identify thermal translational noise is required for bubble generation. Intriguingly, the magnitude of the thermal noise needed for bubble formation can be remarkably small in comparison with the particle activity but cannot be identically zero. The cooperative motion evidenced within the dense phase of the thermal hexatic domains may may be necessary for bubble production.
format Preprint
id arxiv_https___arxiv_org_abs_2603_17320
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Hexatic Order Coupled with Thermal Noise Produces Bubbles in Two-Dimensional Active Matter
Langford, Luke
Omar, Ahmad K.
Soft Condensed Matter
The phase separation of purely-repulsive particles induced by self-propulsion is among the most well-studied non-equilibrium phase transitions. However, some notable features of this transition remain open questions, including the origin of bubbles within the dense phase in two dimensions. Various explanations have been proposed, ranging from a reversal of the Ostwald ripening process to topological defects at the borders of hexatic domains. We present particle-based simulations that disentangle the effect of hexatic domains on the bubble size and number distribution through the introduction of polydispersity. While hexatic order is found to be necessary for bubble formation, we also identify thermal translational noise is required for bubble generation. Intriguingly, the magnitude of the thermal noise needed for bubble formation can be remarkably small in comparison with the particle activity but cannot be identically zero. The cooperative motion evidenced within the dense phase of the thermal hexatic domains may may be necessary for bubble production.
title Hexatic Order Coupled with Thermal Noise Produces Bubbles in Two-Dimensional Active Matter
topic Soft Condensed Matter
url https://arxiv.org/abs/2603.17320