The research results have been published in the Proceedings of the National Academy of Sciences, by the authors Alexandra Zampetaki (Max Planck Institute for Extraterrestrial Physics, Garching), Alexei Benno (Institute for Theoretical Physics, Heinrich Heine University, Düsseldorf) and Hartum Löwen (Institute for Condensed Matter Physics, Technical University of Darmstadt). The reason for seeing physicists investigating penguins is that the research has been carried out from the perspective of the group dynamics of communication between particles, as can be deduced from the title of the article itself: Collective self-optimization of communicating active particles . In the research, the penguins were treated as particles that move in search of the optimum temperature. They made a new model for active particles that can self-direct their direction of motion. These particles communicate with each other when they detect an available resource within the array. This movement together with communication is described by a scalar field of temperature . The effect of this field is that the particles will go to where a more favorable temperature situation is provided at all times.
The Abstract of the work itself begins by stating the following: “The search for how to collectively self-organize to maximize the chances of survival of the members of a social group requires finding an optimal compromise between maximizing the well-being of an individual and that of the group .” The penguins of Antarctica fight against the cold by grouping themselves together, it is something known to all. But it is not true that penguins are always looking for a higher temperature , they will move to find a rise in their current temperature, according to their own body conditions. And that is one of the keys, the constant search for an increase or decrease in temperature, which makes the formation of groups a highly dynamic process ”.
Researchers have found that interaction with the field leads to a concept known as the “three-body force” or “triple forces” between particles. As its name suggests, three-body forces occur only if there are three bodies, not as in the case of the interaction between two masses (gravitation) or two charges (Coulomb). These triple forces are the key to understanding the collective dynamics of active particles communicating with each other. And it is applicable both in groups of penguins that seek to optimize their temperature or bacteria that want to do the same with oxygen consumption. “This concept could serve as a useful ingredient to optimize sets of artificial active agents or to help reveal aspects of the communication rules used by certain social groups to maximize their chances of survival.”
Chemotaxis , for example, “provides one of the simplest but most effective coping mechanisms.” It consists of a phenomenon in which bacteria and other cells of multicellular organisms control their movements based on the concentration of certain chemical substances present in their environment. “Many microorganisms can detect the concentration of a chemical and go up (positive chemotaxis) or down (negative chemotaxis) its gradient.” This mechanism, “which allows them to go towards nutrients and away from dangerous toxins”, is used for intercellular signaling. The E. Coli bacteria and Dictyostelium cells produce collective chemicals when they starve . The rest of the individuals follow the collective chemical gradient and can thus endure long periods of starvation. This has already been studied since the 70s of the 20th century, framed in the classic Patlak-Keller-Segel model. It is taken into account here that the volume of occupation of the space is finite, so the space available in the habitability of the cells that make it up is restricted. Another example of field gradients would be that of the algae Euglena gracilis , which seek optimal levels of light intensity for photosynthesis. This ability is called phototaxy . If the movement is not oriented, we would speak of photophobia or photoshock.
In the case of more complex living systems, the maintenance of optimal conditions (homeostasis) is accompanied by physiological responses, as we have been commenting, but also behavioral. “This introduces a paradigm of social thermoregulation for different species, such as birds, mice and rats, the most notable case being that of penguins.”
The original article has been presented on the website of the Heinrich Heine University (HHU), Düsseldorf, as well as on the official twitter account of said institution.
“Almost all the fundamental laws of physics can be described as a minimization problem, for example that the total energy is minimized,” explained Dr. Hartmut Löwen, director of the Institute at HHU. “On the contrary, there was no minimization in the system we examined. On the other hand, there was an optimization to reach an ideal area ”. This allows us to speak of an internal group dynamic in which there is benefit “for all”, despite being driven by self-interest. Global behavior results in a non-periodic configuration in which individuals with fewer neighbors move closer together to get warmer .
Dr Benno Liebchen from Darmstadt Technical University added: “The interaction between penguins through a collectively created field is reminiscent of how many microorganisms communicate. For example, bacteria that consume oxygen could use a similar optimization principle to achieve the optimal oxygen concentration without having to coordinate their behavior.
Dr. Zampetaki concluded: ” The optimization principle we discovered builds a bridge between physics and biology and shows how quantitative modeling of simple communication rules leads to phenomena that would be unattainable based on ordinary pairing interaction.”
