Collective and emergent behavior of living systems

Choi, Sang Hyun

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https://hdl.handle.net/2142/127430 Copy

Description

Title

Collective and emergent behavior of living systems

Author(s)

Choi, Sang Hyun

Issue Date

2024-08-15

Director of Research (if dissertation) or Advisor (if thesis)

Goldenfeld, Nigel

Doctoral Committee Chair(s)

Maslov, Sergei

Committee Member(s)

• Kim, Sangjin
• Stone, Michael

Department of Study

Physics

Discipline

Physics

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• emergence
• collective behavior
• social network
• non-reciprocity
• chiral
• active matter
• statistical physics
• living systems

Abstract

This dissertation focuses on two aspects of living systems: social networks, and activity and non-reciprocity. Living matter is almost never alone. Life is an emergent result of complex interaction among various agents, and thus a living system can be thought as a community in a general sense; a body of a multicelluar organism, a single cell, and the whole ecosystem are all communities in which the constituents such as cells, organelles, symbionts, preys, predators, etc. interact and produce the functionality of the system. In this dissertation, we consider a more literal community, which is a social system. Through social interaction, the members of a community become connected, which gives rise to a network. Our work investigates the statistical properties that reflect the nature of the interactions present in the networked community with implications for the behavior of the individual agents themselves. On the other hand, the interactions happening in living systems are typically non-reciprocal; two interacting agents influence each other in a different way. In addition, living matter is active, which means that it consumes energy on its own to move. The combination of activity and non-reciprocity leads to unconventional physical properties. This dissertation investigates the unconventional response due to activity and non-reciprocity that would be experimentally realizable in living systems. Part I is about the scaling behavior found in the distribution of interaction duration of honeybees. The analysis of the experimental data collected by our collaborators using automated methods reveals that the distribution of trophallaxis duration in honeybee colonies is heavy-tailed. Here trophallaxis is mouth-to-mouth liquid food transfer that honeybees engage in not only for feeding but also for communicating. We model the termination of each interaction event using the Kramers theory for the escape over a potential barrier that represents the affinity of each of the individuals in the interaction. We demonstrate that the heavy tail in the distribution reflects the heterogeneity in the affinity of individuals within the population. The human face-to-face interaction data from SocioPatterns collaboration are compared with our results with honeybees, and we discovered that that our minimal model built for honeybee social interaction is applicable to human social interactions too, despite the superficial differences between the two systems. In addition, we observe a manifestation of the Gnedenko-Kolmogorov theorem in certain human datasets, where the individual interaction distributions are sufficiently short-ranged that the central limit theorem applies instead of a heavy-tailed distribution for the community interactions. The deduction of individual variations within the honeybee population is a surprising result, and we developed a model-free way to test this conclusion. By applying a method that is independent of our theory, we confirm the existence and nontrivial effect of individual variations in honeybee workers, which have conventionally been neglected in models of eusocial insects. Part II is about odd elastic waves in the living crystal of starfish embryos. The combination of activity, non-reciprocity and chirality gives rise to an unconventional elastic response called odd elasticity; displacement gradients and strains that are independent in conventional materials are coupled in odd materials. The embryos of starfish Patiria miniata form a crystalline cluster during a transient period of their development, and their living crystal has been recently reported to embody odd elasticity. The living crystal also exhibited oscillatory behavior, but the nature of this oscillatory behavior has remained inconclusive. My work analyzes the spectra from current correlation functions, and demonstrates that the oscillatory behavior was due to the combined effect of self-spinning and self-propulsion of the embryos, rather than an odd elastic wave. Self-propulsion had been neglected in the original model of odd solids, but turns out to be important for the elastic response. We show that noise due to self-propulsion can lead to persistent odd elastic waves in this overdamped system and derive the approximate condition for the onset of the stochastic odd elastic wave. Our work underscores the significant contribution of self-propulsion and noise ubiquitous in living systems to the dynamics of active and living matter.

Graduation Semester

2024-12

Type of Resource

Thesis

Handle URL

https://hdl.handle.net/2142/127430

Copyright and License Information

Copyright 2024 Sang Hyun Choi

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