Effects of knotting on the collapse of active ring polymers

Fuente: arXiv
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Main Authors: Breoni, Davide, Locatelli, Emanuele, Tubiana, Luca
Format: Preprint
Published: 2025
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author Breoni, Davide
Locatelli, Emanuele
Tubiana, Luca
author_facet Breoni, Davide
Locatelli, Emanuele
Tubiana, Luca
contents We use numerical simulations to study tangentially active flexible ring polymers with different knot topologies. Simple, unknotted active rings display a transition from an extended phase to a collapsed one upon increasing the degree of polymerization. We find that topology has a significant effect on the polymer size at which the collapse takes place, with twist knots collapsing earlier than torus knots. Increasing knot complexity further accentuates this difference, as the collapse point of torus knots grows linearly with the minimum crossing number of the knot while that of twist knots shrinks, eventually canceling the actively stretched regime altogether. This behavior is a consequence of the ordered configuration of torus knots in their stretched active state, featuring an effective alignment for non-neighboring bonds which increases with the minimal crossing number. Twist knots do not feature ordered configurations or bond alignment, increasing the likelihood of collisions, leading to collapse. These results show that topology yields a degree of control on the properties of active ring polymers, and can be used to tune them. At the same time, they suggest that activity might introduce a bias for torus knots, as complex twist knots cannot be formed in extended active polymers.
format Preprint
id arxiv_https___arxiv_org_abs_2507_08391
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Effects of knotting on the collapse of active ring polymers
Breoni, Davide
Locatelli, Emanuele
Tubiana, Luca
Soft Condensed Matter
Statistical Mechanics
We use numerical simulations to study tangentially active flexible ring polymers with different knot topologies. Simple, unknotted active rings display a transition from an extended phase to a collapsed one upon increasing the degree of polymerization. We find that topology has a significant effect on the polymer size at which the collapse takes place, with twist knots collapsing earlier than torus knots. Increasing knot complexity further accentuates this difference, as the collapse point of torus knots grows linearly with the minimum crossing number of the knot while that of twist knots shrinks, eventually canceling the actively stretched regime altogether. This behavior is a consequence of the ordered configuration of torus knots in their stretched active state, featuring an effective alignment for non-neighboring bonds which increases with the minimal crossing number. Twist knots do not feature ordered configurations or bond alignment, increasing the likelihood of collisions, leading to collapse. These results show that topology yields a degree of control on the properties of active ring polymers, and can be used to tune them. At the same time, they suggest that activity might introduce a bias for torus knots, as complex twist knots cannot be formed in extended active polymers.
title Effects of knotting on the collapse of active ring polymers
topic Soft Condensed Matter
Statistical Mechanics
url https://arxiv.org/abs/2507.08391