The ants go marching in giant number fluctuations
DOI: 10.1063/10.0043770
The ants go marching in giant number fluctuations lead image
Ants have long been employed to study topics from engineering to cooperative problem solving, and now researchers have made discoveries about active matter with the help of fire ants.
Anderson et al. used ants to study a dense active system and quantify their number fluctuations, or deviations from the mean value.
The researchers placed a group of ants in thin disks to model their movements as two-dimensional active systems. Since ants undergo activity cycles from stationary clusters to an overall motion state, the researchers decided to characterize the ant-collective fluctuations in both states. The researchers imaged the ants’ collective dynamics for a few hours at a time and quantified their clustering states as well as overall motions.
“The exciting result is that the fire ant collective clearly exhibits giant number fluctuations,” said author Alberto Fernandez-Nieves. “These giant fluctuations are seen both in the more and the less active states; however, the experimental data clearly suggests that the origin of the giant fluctuations is distinct for each state.”
Since the fluctuations were giant, as in other active systems, they were thus characterized by changes in density that are enhanced relative to what is seen in systems in equilibrium.
The experimental results highlight that while the exponents characterizing giant number fluctuations are similar, they originate differently, such as from clustering or local alignment and motion.
Notably, the scaling exponent for giant number fluctuations seen in the ants was consistent with simulations of polar active particles — ones that are self-propelled in a preferred direction, like bacteria or motile cells — suggesting the ants themselves behave as polar active particles in the ant-collective active state.
Source: “Giant number fluctuations in fire-ant collectives,” by C. J. Anderson, B. Argelich, A. Fernandez-Nieves, Journal of Applied Physics (2026). The article can be accessed at https://doi.org/10.1063/5.0326020 .
