Detecting and characterizing phase transitions in active matter using entropy

A major challenge in the study of active matter lies in quantitative characterization of phases and transitions between them. We show how the entropy of a collection of active objects can be used to classify regimes and spatial patterns in their collective behavior. Specifically, we estimate the con...

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Bibliographic Details
Published in:Soft matter 2023-07, Vol.19 (27), p.5118-5126
Main Authors: Sorkin, Benjamin, Be'er, Avraham, Diamant, Haim, Ariel, Gil
Format: Article
Language:English
Subjects:
Aspect ratio
Entropy
Phase diagrams
Phase transitions
Statistical analysis
Swarming
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Summary:A major challenge in the study of active matter lies in quantitative characterization of phases and transitions between them. We show how the entropy of a collection of active objects can be used to classify regimes and spatial patterns in their collective behavior. Specifically, we estimate the contributions to the total entropy from correlations between the degrees of freedom of position and orientation. This analysis pin-points the flocking transition in the Vicsek model while clarifying the physical mechanism behind the transition. When applied to experiments on swarming Bacillus subtilis with different cell aspect ratios and overall bacterial area fractions, the entropy analysis reveals a rich phase diagram with transitions between qualitatively different swarm statistics. We discuss physical and biological implications of these findings. Experimental snapshots showing swarming Bacillus subtilis bacteria of various aspect ratios at different area fractions. The entropy of cell configurations was used to detect phase transitions.
ISSN:1744-683X
1744-6848
DOI:10.1039/d3sm00482a