Universität zu Köln

Negi, Rajendra Singh ORCID: 0000-0002-6522-166X (2024). Collective phenomenon in active systems with multichannel perception. PhD thesis, Universität zu Köln.

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Abstract

Active matter systems show remarkable self-organization across different scales, from micron-size bacteria to meter-size birds. Examples extend beyond biological systems such as flocks of birds, animal herds, and bacterial biofilms, to artificial systems like active colloids and swarms of microrobots. The global patterns and structures often occur purely based on local interactions among neighbors. Emergent properties and functions go beyond what individual components can achieve on their own. Some important features of such systems are active non-equilibrium behavior, non-reciprocal interactions, information processing, and self-steering. In our model of intelligent active Brownian particles (iABPs), information about the position and orientation of neighboring particles obtained through directed visual and isotropic perception, respectively, is used to adjust the propulsion direction. We start with the role of visual perception, where an iABP can sense the instantaneous position of neighboring iABPs within a vision cone (VC) and vision range. Several non-equilibrium structures like motile worms, worm-aggregate coexistence, aggregates, dilute-gas, and compact or dispersed cluster phases are obtained, depending on the system parameters. The maneuverability due to visual signal, activity, density, vision angle, and vision range determine the location and extent of these phases in the phase diagram. The analysis of the particle’s mean-square displacement shows ABP-like dynamics for dilute systems and the worm phase. We then delve into the interplay of visual perception and alignment interactions. The maneuverability due to visual signal and polar alignment determines the selforganization. Various non-equilibrium dynamical aggregates – like motile worm-like swarms and milling, and compact or dispersed clusters – are obtained. Strong polar alignment favors elongated worm-like swarms, which show super-diffusive motion over a much longer time range than individual ABPs. These swarms also show highly polarised and persistent motion. The behavior of particles for changing maneuverability and vision angle is very similar, and we can capture it by effective maneuverability. Higher maneuverability favors the formation of compact clusters. Milling rings, where swarms bite their own tail, emerge for balanced polar to visual maneuverability, intermediate activity, and vision angles. The study of binary mixtures of iABPs interacting with visual perception shows several intriguing patterns such as dimeric, tetrameric, multimeric phase, hopping, prey-predator behavior, and honeycomb lattice structures. The structures obtained depend on the sign and magnitude of visual maneuverability, activity, vision angles, vision range, and the number of these two types of particles. For opposite attractive and similar repulsive interaction of particles, i.e., particles of type-A are mutually attracted to particles of type-B but repelled by other particles of type-A (similarly for type-B), at nearly the same density, we observe an interesting behavior where an unpaired particle (known as a hopper) shuttles between pairs composed of particles from both types. As the density increases, the average hopping distance covered by these particles decreases. When particles of type-A are attracted to particles of type-B, while particles of type-B simultaneously repel particles of type-A, an intriguing dynamic similar to a prey-predator relationship emerges between the two types. Both the fraction of time spent by prey (type-B) in the vicinity of a predator (type-A), as well as the prey distribution around a predator, indicates focused vision angle \pi/4 and higher steering maneuverability of the predator towards prey is highly effective for the predator to reach prey. We also investigate systems where type-B particles steer toward each other, while type-A particles tend to steer away from other type-B as well as type-A particles; which display the formation of honeycombtype lattices. The average size of the cluster within the honeycomb lattice structure depends upon the vision range and the structure becomes more distinct as the vision range increases. Finally, we consider assembles of actively avoiding particles having visual clues. This model mimics some features of pedestrian behaviors like interpersonal distancing in a dense crowd. A high value of maneuverability ! and a low value of activity Pe favors interpersonal distancing for high vision angles, where the average minimum distance scales Pe^3/2/\Gamma. Also, the average distance to the nearest particles decreases with number density. A higher activity leads to less exposure time where two particles are in close vicinity. For a more focused vision and beyond certain maneuverability, we obtain band-like aggregates that move ballistically over a long time and show highly persistent motion. In summary, our results help to understand the collective behavior of cognitive self-propelled particles, like animal herds, swarming bacteria, and non-reciprocally interacting prey-predator systems like fish schools, and provide new insights for the design of micro-robotic swarms. Our model can also be employed to study pedestrian behavior in semi-dense crowds.

Item Type:	Thesis (PhD thesis)
Creators:	Creators Email ORCID ORCID Put Code Negi, Rajendra Singh negibhai97@gmail.com orcid.org/0000-0002-6522-166X UNSPECIFIED
Contributors:	Contribution Name Email Author Negi, Rajendra Singh negibhai97@gmail.com
URN:	urn:nbn:de:hbz:38-740523
Date:	2024
Language:	English
Faculty:	Faculty of Mathematics and Natural Sciences
Divisions:	Außeruniversitäre Forschungseinrichtungen > Forschungszentrum Jülich
Subjects:	Natural sciences and mathematics Physics
Uncontrolled Keywords:	Keywords Language Active Matter English Soft Matter English Visual Perception English Active Brownian Particles English Alignment interaction English Non-reciprocal interaction English Microswimmers English
Date of oral exam:	12 March 2024
Referee:	Name Academic Title Gompper, Gerhard Prof. Dr. Schadschneider, Andreas Prof. Dr.
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/74052