Persistent noise-driven odd elastic waves in living chiral active matter
Chirality
and activity lead to non-reciprocal transverse interaction between
neighboring particles. Then peculiar elasticity called "odd
elasticity" emerges, represented by off-diagonal asymmetric elements
in the elastic modulus tensor. The predicted odd elastic waves are
expected to be difficult to experimentally observe because of damping
due to longitudinal interaction. Inspired by fluctuation-driven
pattern formations in population dynamics, we generate persistent odd
elastic waves driven by noise due to self-propulsion. We focus on the
model of starfish embryos Patiria miniata, which form a
living crystal during a certain stage of their development. This
living crystal has been experimentally shown to be odd-elastic. By
adding the noise from collision between neighbors due to
self-propulsion, which has been neglected in previous works, we
demonstrate that the wave persists even in the presence of damping.
Our derivation of the new criterion for persistent noise-driven odd
elastic wave and the numerically constructed phase diagram suggest
that strong enough, but not too strong, noise and transverse force
relative to longitudinal force are needed for the persistent wave.
Although our work focuses on the starfish embryos, our framework is
general and is applicable to other chiral active systems.
S.H. Choi, Z.-F. Huang and N. Goldenfeld. "Noise-driven odd elastic waves in living chiral active matter," arXiv:2411.09615 [cond-mat.soft] [link]
The scaling behavior in honeybee and human social interaction
Burstiness
of an inter-event time distribution has been much studied because of
its relation to information or disease spreading. On the other hand,
the distribution of contact duration has received less attention. We
measured the duration of honeybee trophallaxis, or mouth-to-mouth
liquid food transfer, and face-to-face encounters by using
high-resolution tracking in collaboration with Robinson Lab in the University of Illinois and
found out that the distribution of event durations is
heavy-tailed. Human data recorded by the SocioPatterns collaboration show that human
face-to-face interactions in various settings also exhibit a
heavy-tailed interaction time distribution. Such similarity across
different systems suggests unexpected universality in social
interactions. We have derived the power-law form by building a minimal
model that treats the termination of an interaction as a particle
escaping over an energy barrier; the variability in the population
leads to a distribution of energy barriers which is determined by the
extreme value theory and is a key to achieving the final power-law
form. Honeybees indeed exhibit individual differences in interactivity
although they are less different than humans. Our work demonstrates
how individual differences can lead to universal patterns of social
interaction that transcend species, context and specific mechanisms.
S.H. Choi, V.D. Rao, T. Gernat, A.R. Hamilton, G.E. Robinson and N. Goldenfeld. "Individual variations lead to universal and cross species patterns of social behavior," Proc. Natl. Acad. Sci. 117, 31754-31759 (2020) [link]