# gst: apropos of collective behaviors, a visual model to reproduces swarming, schooling, and milling.

<< Animal collective behavior is often modeled with self-propelled particles, assuming each individual has “omniscient” knowledge of its neighbors. Yet, neighbors may be hidden from view and we do not know the effect of this information loss. To address this question, (AA) propose a visual model of collective behavior where each particle moves according to bioplausible visual cues, in particular the optic flow. This visual model successfully reproduces three classical collective behaviors: swarming (no orientational order), schooling (high orientational order), and milling (the group coordinately swirls in a circular pattern). >>️

Diego Castro, Franck Ruffier, Christophe Eloy. Modeling collective behaviors from optic flow and retinal cues. Phys. Rev. Research 6, 023016. Apr 4, 2024. 

https://journals.aps.org/prresearch/abstract/10.1103/PhysRevResearch.6.023016

Also: swarm, flock, behav, particle, in https://www.inkgmr.net/kwrds.html 

Keywords: gst, swarming, flocking, behavior, particle, self-propelled particles

# gst: apropos of evaporation, puncturing of active drops

<< By virtue of self-propulsion, active particles impart intricate stresses to the background fluids. (..) this active stress can be utilized to greatly control evaporation dynamics of active drops. >>

AA << discover a new phenomenon of puncturing of the active drops, where the air-liquid interface of the drop undergoes spontaneous tearing and there occurs a formation of a new three-phase contact line due to the liquid-air interface hitting the liquid-solid interface through evaporation-driven mass loss. Post puncturing, (AA) see an inside-out evaporation of the drop, where the new contact line sweeps towards the pinned outer contact line of the drops, contrasting regular drops that straightaway shrink to zero volume with self-similar shape. >>

<< Furthermore, (..) the activity inside the drops can manipulate the three-phase contact-line dynamics, which for contractile drops can result in an up to 50% enhanced lifetime of the drop and 33% quicker evaporation for extensile drops. By analyzing the flux distribution inside the drop, (AA) gain insights on nonintuitive deposition patterns (e.g., ring galaxy type deposits that demonstrate controllable spatial gradients in the concentrations of the deposited particles) of active particles, which are oftentimes biological substances or bimetallic nanoparticles of interest. >>

Ghansham Rajendrasingh Chandel, Vishal Sankar Sivasankar, Siddhartha Das. Evaporation of active drops: Puncturing drops and particle deposits of ring galaxy patterns. Phys. Rev. Fluids 9, 033603. Mar 27, 2024. 

https://journals.aps.org/prfluids/abstract/10.1103/PhysRevFluids.9.033603

Also: drop, particle, evaporation, transition, in https://www.inkgmr.net/kwrds.html 

Keywords: gst, drop, particle, evaporation, transition, drop interactions, droplet, droploid

# gst: soft and stiff modes in colloidal particle networks

<< Floppy microscale spring networks are widely studied in theory and simulations, but no well-controlled experimental system currently exists. >> 

AA << show that square lattices consisting of colloid-supported lipid bilayers functionalized with DNA linkers act as microscale floppy spring networks. (AA) extract their normal modes by inverting the particle displacement correlation matrix, showing the emergence of a spectrum of soft modes with low effective stiffness in addition to stiff modes that derive from linker interactions. >>

<< Evaluation of the softest mode, a uniform shear mode, reveals that shear stiffness decreases with lattice size. >>

 AA << results reveal the importance of entropic steric effects. >>

️

Julio Melio, Silke E. Henkes, Daniela J. Kraft. Soft and Stiff Normal Modes in Floppy Colloidal Square Lattices. Phys. Rev. Lett. 132, 078202. Feb 14, 2024. 

https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.132.078202

Also: particle, nano, colloids, network, in https://www.inkgmr.net/kwrds.html

Keywords: gst, particle, nano, colloids, network, colloidal network

# gst: transitions in disordered medium.

AA << study computationally the dynamics of forced, Brownian particles through a disordered system. As the concentration of mobile particles and/or fixed obstacles increase, (AA) characterize the different regimes of flow and address how clogging develops. >>️

AA << show that clogging is preceded by a wide region of anomalous transport, characterized by a power law decay of intermittent bursts. (..) this abnormal flow region is characterized by a coexistence between mobile and arrested particles, and their relative populations change smoothly as clogging is approached. >>

️

Sergi G. Leyva, Ignacio Pagonabarraga. Clogging transition and anomalous transport in driven suspensions in a disordered medium. Phys. Rev. E 109, 014618. Jan 31, 2024.

https://journals.aps.org/pre/abstract/10.1103/PhysRevE.109.014618

img:  https://twitter.com/PhysRevE/status/1753068208586711072   

Also: transition, particle, disorder, in https://www.inkgmr.net/kwrds.html

Keywords: gst, transition, particle, disorder

# gst: intertwining order, disorder, and hierarchy

<< Nature hosts a wealth of materials showcasing intricate structures intertwining order, disorder, and hierarchy, delivering resilient multifunctionality surpassing perfect crystals or simplistic disordered materials. The engineering of such materials through nanoparticle assembly represents a burgeoning field, poised with potential to yield sustainable material systems rivaling or exceeding biological functionalities. >>

AA << review delineates the fundamental concept of complexity in the context of nanoscale materials. >>

Xiaoming Mao, Nicholas Kotov. Complexity, Disorder, and Functionality of Nanoscale Materials. arXiv: 2401.09567v1 [cond-mat.soft]. Jan 17, 2024. 

https://arxiv.org/abs/2401.09567

Also: nano, particle, order, disorder, in  https://www.inkgmr.net/kwrds.html

Keywords: nano, particle, order, disorder 

# gst: pulsating active matter.

<< the mechanical pulsation of locally synchronized particles is a generic route to propagate deformation waves. >>

️

AA << consider a model of dense repulsive particles whose activity drives periodic change in size of each individual. >>️

They << show that the competition between repulsion and synchronization triggers an instability which promotes a wealth of dynamical patterns, ranging from spiral waves to defect turbulence. >>️

Yiwei Zhang, Etienne Fodor. Pulsating Active Matter. Phys. Rev. Lett. 131, 238302. Dec 8, 2023. 

https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.131.238302

Also: waves, particle, transition, instability, turbulence, in https://www.inkgmr.net/kwrds.html 

Keywords: gst, waves, particle, transition, instability, turbulence

# gst: scanning inside a granular raft

<< Rheology of macroscopic particle-laden interfaces, called “granular rafts,” has been experimentally studied in the simple shear configuration.  >>️

<< Close to the walls of the rheometer cell, one can observe regions of large local shear rate while in the middle of the cell a quasistatic zone exists. >>

<< Measuring the probability density functions of the instantaneous local shear rate, (AA) provide evidence of a balance between positive and negative instantaneous local shear rate. This behavior is the signature of a quasistatic region inside the granular raft. >>️

️

J. Lalieu, A. Seguin, G. Gauthier. Rheology of granular rafts. Phys. Rev. E 107, 064901. June 29, 2023.

https://journals.aps.org/pre/abstract/10.1103/PhysRevE.107.064901

Also: Bavand Keshavarz, Michela Geri. Mandelbrot granular raft. Phys. Rev. Fluids 8, 110506. Nov 16, 2023.

https://journals.aps.org/prfluids/abstract/10.1103/PhysRevFluids.8.110506

Also: grain, particle, in https://www.inkgmr.net/kwrds.html 

Also: << l'invasiva scorribanda /

sull' oramai alla deriva lacerata randa. >>️ in: Schismi da vibrati di tangone. Notes. March 23, 2005. (quasi-stochastic poetry)

https://inkpi.blogspot.com/2005/03/1608b-schismi-da-vibrati-di-tangone.html

Keywords: gst, raft, particle, grain, granular raft, life

# gst: local elastic properties of strongly disordered matter

<< The local elastic properties of strongly disordered material are investigated using the theory of correlated random matrices. A significant increase in stiffness is shown in the interfacial region, the thickness of which depends on the strength of disorder. It is shown that this effect plays a crucial role in nanocomposites, in which interfacial regions are formed around each nanoparticle. >>️

D. A. Conyuh, A. A. Semenov, Y. M. Beltukov. Effective elastic moduli of composites with a strongly disordered host material. Phys. Rev. E 108, 045004. Oct 20, 2023. 

https://journals.aps.org/pre/abstract/10.1103/PhysRevE.108.045004

Also: elastic, noise, particle, nano, in https://www.inkgmr.net/kwrds.html

Keywords: gst, elastic, noise, particle, nano

# gst: emergence of self-organizing zigzag patterns among (magnetic) particles suspended in a liquid

<< When molecules or bacteria organize into a long-range pattern, researchers want to understand how the microscopic interactions lead to the macroscopic order. (AA) observed such self-organization in magnetic particles suspended in a liquid and subjected to an oscillating magnetic field. Through experiments and simulations, the team showed that the resulting zigzag pattern is explained by the fluid flow generated around the oscillating particles, not by any details of the particles or the applied field. Similar zigzag patterns have also been seen in charged colloids subjected to oscillating electric fields, so the explanation may cover a range of particle systems. The researchers also believe that understanding and controlling the effect could lead to useful applications in microfluidics devices. >>️

David Ehrenstein. Self-Organized Zigzags from Fluid Flow. Physics 16, 138. Aug 11, 2023.

https://physics.aps.org/articles/v16/138

Gaspard Junot, Marco De Corato, Pietro Tierno. Large Scale Zigzag Pattern Emerging from Circulating Active Shakers. Phys. Rev. Lett. 131, 068301. Aug 11, 2023. 

https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.131.068301

Also: particle, self-assembly, chiral, behav, in: https://www.inkgmr.net/kwrds.html  

Keywords: gst, behavior, particle, self-assembly, self-organization, chiral, active shakers, squirmers, alternating chirality

# gst: stochastic resonance mediated by optimal noise level values; transport of colloidal particles induced by substrate concentration oscillations.

AA << show the existence of a  stochastic resonant regime in the transport of active colloidal particles under confinement. The periodic addition of substrate to the system causes the spectral amplification to exhibit a maximum for an optimal noise level value. The consequence of this is that particles can travel longer distances with lower fuel consumption. The stochastic resonance phenomenon found allows the identification of optimal scenarios for the transport of active particles, enabling them to reach regions that are otherwise difficult to access, and may therefore find applications in transport. >>️

J. D. Torrenegra-Rico, A. Arango-Restrepo, J. M. Rubi. Optimal transport of active particles induced by substrate concentration oscillations. Phys. Rev. E 108, 014134. July 28, 2023.

https://journals.aps.org/pre/abstract/10.1103/PhysRevE.108.014134

Img: https://twitter.com/PhysRevE/status/1687119409096089602

Also: particle, colloids, noise, in:  https://www.inkgmr.net/kwrds.html

Keywords: gst, particle, colloids, noise, stochastic resonance, substrate oscillation

# gst: inertial particles within co-rotating dusty vortices

 << dispersed particles with moderate inertia cause the vortex pair to push apart to a separation nearly twice as large as the initial separation. >>

 

 << antisymmetric vorticity generated by particles flung out of the rotational cores causes the vortex pair repulsion. Eventually, the two dusty vortices merge into a single vortex with most particles accumulating outside the core similar to the dusty Lamb-Oseen vortex described in Shuai & Kasbaoui (2022) >>

 

 << For weakly inertial particles, (AA) find that the merger dynamics follow the same mechanics as those of a single-phase flow, albeit with a density that must be adjusted to match the mixture density. >>

 

<< Lastly, highly inertial particles tend to fragment the vortex cores leading to murky merger dynamics. >>

Shuai Shuai, Anubhab Roy, M. Houssem Kasbaoui. The merger of co-rotating vortices in dusty flows. arXiv: 2307.05413v1 [physics.flu-dyn]. Jul 11, 2023. 

https://arxiv.org/abs/2307.05413

Also: particle, vortex, in https://www.inkgmr.net/kwrds.html

Keywords: gst, particle, vortex 

# gst: the effects of order- disorder on a system of swarmalators that move on a one-dimensional ring.

<< Swarmalators are phase oscillators that cluster in space, like fireflies flashing on a swarm to attract mates. >>

<< In this work, (AA) explore the effects of disorder induced by phase frustration on a system of Swarmalators that move on a one-dimensional ring. >>

They find << numerically and analytically, the ordered and disordered states that emerge in the system. The active states, not present in the model without disorder, resemble states found previously in numerical studies for the 2D Swarmalators system. One of these states, in particular, shows similarities to turbulence generated in a flattened media. (AA) show that all ordered states can be generated for any values of the coupling constants by tuning the phase frustration parameters only. Moreover, many of these combinations display multi-stability. >>️

Joao U.F. Lizarraga, Marcus A.M. de Aguiar. Sakaguchi Swarmalators. arXiv: 2305.08615v1 [nlin.PS]. May 15, 2023. 

https://arxiv.org/abs/2305.08615

Also:  'swarm', 'turbulence', 'noise', 'particle' in: https://www.inkgmr.net/kwrds.html

Keywords: gst, swarm, turbulence, noise, particle

# gst: intricate transitions in elastoactive structures.

<< The interplay between activity and elasticity often found in active and living systems triggers a plethora of autonomous behaviors ranging from self-assembly and collective motion to actuation. Among these, spontaneous self-oscillations of mechanical structures is perhaps the simplest and most widespread type of nonequilibrium phenomenon. >>️

<< Here, (AA) introduce a centimeter-sized model system for one-dimensional elastoactive structures. >>️

<< such structures exhibit flagellar motion when pinned at one end, self-snapping when pinned at two ends, and synchronization when coupled together with a sufficiently stiff link. (..) these transitions can be described quantitatively by simple models of coupled pendula with follower forces. >>️

Ellen Zheng, Martin Brandenbourger, et al. Self-Oscillation and Synchronization Transitions in Elastoactive Structures. Phys. Rev. Lett. 130, 178202. April 25, 2023. 

https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.130.178202

Also:  transition, particle, self-assembly, elastic, pendulum in https://www.inkgmr.net/kwrds.html

Keywords: gst, transition, particle, self-assembly, elastic, pendulum

# gst: emergent organization and polarization due to active fluctuations.

AA << introduce and study a model of active Brownian motion with multiplicative noise describing fluctuations in the self-propulsion or activity. (They) find that the standard picture of density accumulation in slow regions is qualitatively modified by active fluctuations, as stationary density profiles are generally not determined only by the mean self-propulsion speed landscape. As a result, activity gradients generically correlate the particle self-propulsion speed and orientation, leading to emergent polarization at interfaces pointing either towards dense or dilute regions depending on the amount of noise in the system.  >>

️

Benoit Mahault, Prakhar Godara, Ramin Golestanian. Emergent organization and polarization due to active fluctuations. Phys. Rev. Research 5, L022012. April 12, 2023. 

https://journals.aps.org/prresearch/abstract/10.1103/PhysRevResearch.5.L022012

Also: 'particle', 'fluctuations', 'noise', 'self-assembly' in https://www.inkgmr.net/kwrds.html

Keywords: gst, particle, organization, polarization, fluctuations, noise, self-propulsion, self-assembly 

# gst: two steady collective states in swarmalators with delayed interactions

AA << investigate the effects of delayed interactions in a population of "swarmalators", generalizations of phase oscillators that both synchronize in time and swarm through space. >>

AA << discover two steady collective states: a state in which swarmalators are essentially motionless in a disk arranged in a pseudo-crystalline order, and a boiling state in which the swarmalators again form a disk, but now the swarmalators near the boundary perform boiling-like convective motions. >>️

Nicholas Blum, Andre Li, et al. Swarmalators with delayed interactions. arXiv: 2210.11417v1 [nlin.AO]. Oct 20, 2022. https://arxiv.org/abs/2210.11417

Also

keyword 'swarm' in FonT

https://flashontrack.blogspot.com/search?q=swarm

keyword 'particle' | 'quasiparticle' in FonT

https://flashontrack.blogspot.com/search?q=particle

https://flashontrack.blogspot.com/search?q=quasiparticle

keyword 'particelle' in Notes

(quasi-stochastic poetry)

https://inkpi.blogspot.com/search?q=particelle

Keywords: gst, particle, swarm

# gst: multiple external fields can modulate confined active particles

AA << analyze a dilute suspension of active particles confined between walls and subjected to fields that can modulate particle speed as well as orientation. Generally, the particle distribution is different in the bulk compared to near the walls. In the bulk, particles tend to accumulate in the regions of low speed, but in the presence of an orienting field, particles rotate to align with the field and accumulate downstream in the field direction. At the walls, particles tend to accumulate pointing into the walls and thereby exert pressure on walls. But the presence of strong orienting fields can cause the particles to reorient away from the walls >>

<< The pressure at the walls depends on the wall separation and the field strengths. This work demonstrates how multiple fields with different functionalities can be used to control active matter under confinement. >>️

Vaseem A. Shaik, Zhiwei Peng, et al. Confined active matter in external fields. arXiv:2208.09797v1 [cond-mat.soft]. Aug 21, 2022. https://arxiv.org/abs/2208.09797 

Also

keyword 'particle' | 'quasiparticle' in FonT

https://flashontrack.blogspot.com/search?q=particle

https://flashontrack.blogspot.com/search?q=quasiparticle

keyword 'particelle' in Notes

(quasi-stochastic poetry)

https://inkpi.blogspot.com/search?q=particelle

Keywords: gst, particle, particle control

# phys: apropos of transitions, even a tiny wobble may reshape theoretical views of the universe

<< The long-awaited first results from the Muon g-2 experiment at the U.S. Department of Energy’s Fermi National Accelerator Laboratory show fundamental particles called muons behaving in a way that is not predicted by scientists’ best theory, the Standard Model of particle physics. >>️

<< Like electrons, muons act as if they have a tiny internal magnet. In a strong magnetic field, the direction of the muon’s magnet precesses, or wobbles, much like the axis of a spinning top or gyroscope. The strength of the internal magnet determines the rate that the muon precesses in an external magnetic field and is described by a number that physicists call the g-factor. This number can be calculated with ultra-high precision. >>

<< The first result from the Muon g-2 experiment at Fermilab confirms the result from the experiment performed at Brookhaven National Lab two decades ago. Together, the two results show strong evidence that muons diverge from the Standard Model prediction. >>

<< The accepted theoretical values for the muon are:

g-factor: 2.00233183620(86)

anomalous magnetic moment: 0.00116591810(43)

[uncertainty in parentheses]

The new experimental world-average results announced by the Muon g-2 collaboration today are:

g-factor: 2.00233184122(82)

anomalous magnetic moment: 0.00116592061(41)

The combined results from Fermilab and Brookhaven show a difference with theory at a significance of 4.2 sigma, a little shy of the 5 sigma (or standard deviations) that scientists require to claim a discovery but still compelling evidence of new physics. The chance that the results are a statistical fluctuation is about 1 in 40,000. >>️

We’re thrilled to announce that the first results from Fermilab’s Muon g-2 experiment strengthen evidence of new physics! #gminus2

https://t.co/tUx4ojzIps https://t.co/t1ufui2Mwu   

17:01  Apr 7,  2021

https://twitter.com/Fermilab/status/1379811596755681286

Tracy Marc. First results from Fermilab’s Muon g-2 experiment strengthen evidence of new physics. Apr 7, 2021.

https://news.fnal.gov/2021/04/first-results-from-fermilabs-muon-g-2-experiment-strengthen-evidence-of-new-physics

Also

Themis Bowcock, Mark Lancaster. How we found hints of new particles or forces of nature – and why it could change physics. Apr 8, 2021.

 

https://theconversation.com/how-we-found-hints-of-new-particles-or-forces-of-nature-and-why-it-could-change-physics-158564

B. Abi et al. (Muon g−2  Collaboration)

 Measurement of the Positive Muon Anomalous Magnetic Moment to 0.46 ppm. Phys. Rev. Lett. 126, 141801. Apr 7, 2021.

https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.126.141801

A primer in particle physics:

Jonathan Carroll. Explainer: Standard Model of Particle Physics. Aug 25, 2011.

https://theconversation.com/explainer-standard-model-of-particle-physics-2539

a 'cartouche' of the Standard Model 

https://images.theconversation.com/files/2516/original/sml_small.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=1055&fit=crop&dpr=3