# gst: collective patterns generated by capillary surfers.

<< Millimeter-sized “surfers” can self-propel across a vibrating liquid surface, interacting with other surfers to create collective patterns. >>

<< Self-propelled objects can move in mesmerizing patterns. The collective movements of groups of such objects typically occur in one of two flow regimes: the inertial regime—think swirling schools of fish in water—or the viscous regime—think swarming colonies of bacteria in mucus. Some self-propelled objects can travel in both flow regimes, a possibility that is less explored. >>️

AA << have studied the motion of a new system of self-propelled objects that move in this intermediate regime, finding that the objects organize into several distinct and tunable motion patterns. >>️️

<< Pairs of self-propelled surfers observed by the team move in one of seven different patterns (the video shows five). These include the “orbit,” where a pair of surfers rotate around a central point; the “tailgate,” where one surfer closely follows another, head to tail in a linear path; and the “jackknife,” where a pair of perpendicular surfers rotate stern to stern around their collision point. >>

<< When only one surfer was present, these mismatched amplitudes propelled the surfer in the direction of its bow. When there were two surfers close to each other, interactions among the waves caused the surfers to either repel each other so that they moved in opposite directions or to come together so that they collectively traced one of seven distinct patterns. >>️

️

Maggie Hudson. Synchronized Surfing of Self-Propelled Particles. Physics 16, s156. Nov 7, 2023. 

https://physics.aps.org/articles/v16/s156

Ian Ho, Giuseppe Pucci, Anand U. Oza, Daniel M. Harris. Capillary surfers: Wave-driven particles at a vibrating fluid interface. Phys. Rev. Fluids 8, L112001. Nov 7, 2023.

https://link.aps.org/doi/10.1103/PhysRevFluids.8.L112001

Anand U. Oza, Giuseppe Pucci, Ian Ho, Daniel M. Harris. Theoretical modeling of capillary surfer interactions on a vibrating fluid bath. Phys. Rev. Fluids 8, 114001. Nov 7, 2023.

https://link.aps.org/doi/10.1103/PhysRevFluids.8.114001

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

Keywords: gst, waves, wave-wave, capillary waves, particles, self-propelled particles, fluid-particle interactions, wave-particle interactions

# 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: to create standing waves induced by mismatches

<< In work recently published (..), the mismatch of electronic momentum across domain walls (i.e., regions with a different orientation of the intrinsic electric dipole) is shown to create standing waves, even though there is no potential buildup across the domain wall. >>

Researchers demonstrate new properties of atomically thin ferroelectrics. University of Arkansas.  May 28, 2019

https://m.phys.org/news/2019-05-properties-atomically-thin-ferroelectrics.html  

Kai Chang, Brandon J. Miller, et al. Standing Waves Induced by Valley-Mismatched Domains in Ferroelectric SnTe Monolayers. Phys. Rev. Lett. 122, 206402 May 24, 2019.

https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.122.206402   

# brain: spiral waves at the edge of neural tissue during cognitive processing.

AA << have discovered human brain signals travelling across the outer layer of neural tissue that naturally arrange themselves to resemble swirling spirals. >>️

<< The research (..) indicates these ubiquitous spirals, which are brain signals observed on the cortex during both resting and cognitive states, help organise brain activity and cognitive processing. >>️

<< Our study suggests that gaining insights into how the spirals are related to cognitive processing could significantly enhance our understanding of the dynamics and functions of the brain, (..) These spiral patterns exhibit intricate and complex dynamics, moving across the brain’s surface while rotating around central points known as phase singularities. >> Pulin Gong.

<< One key characteristic of these brain spirals is that they often emerge at the boundaries that separate different functional networks in the brain, >> Yiben Xu. 

Philip Ritchie. Scientists discover spiral-shaped signals that organise brain activity. sydney.edu.au. Jun 16, 2023. 

https://www.sydney.edu.au/news-opinion/news/2023/06/16/scientists-discover-spiral-shaped-signals-that-organise-brain-activity.html

https://youtu.be/YZlqokljqY8️

Yiben Xu, Xian Long, Jianfeng Feng & Pulin Gong. Interacting spiral wave patterns underlie complex brain dynamics and are related to cognitive processing. Nat Hum Behav. doi: 10.1038/ s41562-023-01626-5. Jun 15,  2023.

https://www.nature.com/articles/s41562-023-01626-5

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

Keywords: brain, vortex, waves,  cognition

# s-brain: hacking inside (slow gamma) rhythms

<< Brain cells share different kinds of information with one another using a variety of different brain waves, analogous to the way radio stations broadcast on different frequencies. >>

<< one of these frequencies allows us to play back memories — or envision future activities — in fast forward. >>

<< fast gamma rhythms encode memories about things that are happening right now; these waves come rapidly one after another as the brain processes high-resolution information in real time. The scientists learned that slow gamma rhythms — used to retrieve memories of the past, as well as imagine and plan for the future — store more information on their longer waves, contributing to the fast-forward effect as the mind processes many data points with each wave. >>

<< The finding has implications for medicine as well as for criminal justice and other areas where memory reliability can be at issue. >>

https://scienmag.com/scientists-discover-how-we-play-memories-in-fast-forward/

Chenguang Zheng, Laura Lee Colgin. Beta and Gamma Rhythms Go with the Flow. Open Archive. Neuron , Volume 85 , Issue 2 , 236 - 237. DOI: http://dx.doi.org/10.1016/j.neuron.2014.12.067

http://www.cell.com/neuron/abstract/S0896-6273(14)01176-3

# art: pictures of the floating world, a guide to making shadow puppets

<< Hiroshige (Utagawa Hiroshige) lived in the 19th century, the end of the classical period of ukiyo-e, the art of woodblock-printed “pictures of the floating world.” In that time he became one of the form’s last masters, having cultivated not just a high level of artistic skill but a formidable productivity. In total, Hiroshige produced more than 8,000 works. >>️

<< But his mastery encompassed more than the urban and rural landscapes of his homeland, as evidenced by this much humbler project: a set of omocha-e, or instructional pictures for children, explaining how to make shadow puppets. >>️

Hiroshige, Master of Japanese Woodblock Prints, Creates a Guide to Making Shadow Puppets for Children (1842). Art, History. Jul 6th, 2021. 

https://www.openculture.com/2021/07/hiroshige-shadow-puppets.html  

Utagawa Hiroshige. Art Institute of Chicago. 

https://www.artic.edu/artists/34946/utagawa-hiroshige

Also

keyword 'fluttuante' in Notes

(quasi-stochastic poetry)

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

keyword 'floating' in FonT

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

keyword 'onda' in Notes 

(quasi-stochastic poetry)

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

keyword 'waves' in FonT

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

Keywords: arts, puppets, shadow puppets, floating worlds, waves

# gst: droplets scoot like caterpillars.

<< From swells in an ocean to ripples in a puddle, the shearing effect of wind blowing over a liquid is visible at all scales. This shear determines the interactions between Earth’s atmosphere and its surface water and, researchers now explain, the movement of liquid droplets that crawl up and down the window of a moving car in the rain. In a series of experiments, (AA) show that airflow triggers surface waves that cause such droplets to crawl like caterpillars before they break apart. >>️

<< At first, the airflow across the droplet’s surface caused the droplet to extend into an oval shape. The droplet also began to tilt, with the liquid piling up at the droplet’s downwind edge. When the drag force exerted by the airflow overcame the capillary force between the glycerin and the glass, the droplet began to slide and to stretch out even more. Surface waves then developed on the elongated droplet and traveled toward its leading edge. The waves induced a stable caterpillar-like motion, with the droplet stretching and contracting along its length. Eventually, beyond a threshold length that depended on the droplet’s volume, the caterpillar was no longer able to withstand the shearing force and broke into several droplets. >>️

AA << say that the behavior follows the same pattern as that of an elongated droplet sliding along an incline. >>

️

Rachel Berkowitz. Droplets Scoot Like Caterpillars. Physics 16, s110. Sep 1, 2023.

https://physics.aps.org/articles/v16/s110  

A. Chahine, J. Sebilleau, R. Mathis, D. Legendre. Caterpillar like motion of droplet in a shear flow. Phys. Rev. Fluids 8, 093601. Sep 1, 2023.

https://journals.aps.org/prfluids/abstract/10.1103/PhysRevFluids.8.093601

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

Keywords: gst, drop, droplet, droploid, bubble, transition

# gst astro: when a superbubble can generate trains of shock waves

<< Sixty-seven million light-years away, a galaxy is blowing enormous bubbles. We know what they are. Known as nuclear superbubbles, the structures are likely created by the supermassive black hole in the galaxy's centre. Now, thanks to new data, we know something incredible is occurring inside them. >>

<< Observations from NASA's Chandra X-ray Observatory of spiral galaxy NGC 3079 have revealed that the bubbles are actually a huge cosmic particle accelerator, producing energetic high-speed particles around their edges.  >>

<< As the bubbles expand into the surrounding gas of the interstellar medium, they generate shock waves, which in turn produce tangled magnetic fields. (..)  particles ricochet around these shock magnetic fields; when they pass through the shock front, they get an acceleration boost.  >>

Michelle Starr. Astronomers Have Found 'Superbubbles' Producing Shock Waves in Another Galaxy.  Mar 4, 2019.

https://www.sciencealert.com/colossal-bubbles-blown-by-a-supermassive-black-hole-are-a-cosmic-particle-accelerator

Jiang-Tao Li, Edmund Hodges-Kluck, et al. Detection of non-thermal hard X-ray emission from the "Fermi bubble" in an external galaxy.  ApJ in press. arXiv:1901.10536v1 [astro-ph.HE] Jan 31, 2019.

https://arxiv.org/abs/1901.10536

# gst: a case of noise-induced excitation wave (in coupled FH-N eq.)

<< There are various research topics such as stochastic resonance, coherent resonance, and neuroavalanche in excitable systems under external noises. >>️

AA << have studied the propagation of excitation waves in the coupled noisy FitzHugh-Nagumo equations with a one-dimensional pacemaker region and found that there is a phase-transition-like phenomenon from the short-range propagation to the whole-system propagation by changing the noise strength T.  >>️

Hidetsugu Sakaguchi. Noise-induced excitation wave and its size distribution in coupled FitzHugh-Nagumo equations on a square lattice. Phys. Rev. E 109, 044211. Apr 19, 2024.

https://journals.aps.org/pre/abstract/10.1103/PhysRevE.109.044211

Also: waves, noise, transition, in https://www.inkgmr.net/kwrds.html 

Keywords: gst, waves, noise, transition

# gst: apropos of transitions, three distinct new families of long-wave instabilities and potential new pathways to turbulence.

AA << reveal three previously unknown instabilities, distinct from the well-known Kelvin-Helmholtz Instability (KHI) and Holmboe Wave Instability (HWI), in that they have longer wavelengths (..) and often slower growth rates. >>

<< The circumstances under which turbulence can persist in strongly stratified flows remains a fascinating debate within the community. [AA] demonstrated that weakly unstable (very) long waves may trigger turbulence and mixing after long periods of time, even under initially very strongly stratified conditions. >>

Lu Zhu, Amir Atoufi, Adrien Lefauve, Rich R. Kerswell, P. F. Linden. Long-wave instabilities of sloping stratified exchange flows. arXiv:2309.10056v1 [physics.flu-dyn]. Sep 18, 2023.

https://doi.org/10.48550/arXiv.2309.10056

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

Keywords: gst, waves, instability, long-wave instability, transition, turbulence, chaos

# brain: the hypothesis that a brain organoid (a lab-grown brain) can reach consciousness.

<< In Alysson Muotri’s laboratory, hundreds of miniature human brains, the size of sesame seeds, float in Petri dishes, sparking with electrical activity. 

These tiny structures, known as brain organoids, are grown from human stem cells and have become a familiar fixture in many labs that study the properties of the brain. Muotri, a neuroscientist at the University of California, San Diego (UCSD), has found some unusual ways to deploy his. He has connected organoids to walking robots, modified their genomes with Neanderthal genes, launched them into orbit aboard the International Space Station, and used them as models to develop more human-like artificial-intelligence (AI) systems. (..) But one experiment has drawn more scrutiny than the others. In August 2019, Muotri’s group published a paper in Cell Stem Cell (*) reporting the creation of human brain organoids that produced coordinated waves of activity, resembling those seen in premature babies. The waves continued for months before the team shut the experiment down. This type of brain-wide, coordinated electrical activity is one of the properties of a conscious brain. >> 

Sara Reardon. Can lab-grown brains become conscious? Nature 586, 658-661. doi: 10.1038/ d41586-020-02986-y. Oct 27, 2020. Correction Nov 4, 2020.

https://www.nature.com/articles/d41586-020-02986-y     

(*)  Trujillo CA, Gao R, et al. Complex Oscillatory Waves Emerging from Cortical Organoids Model Early Human Brain Network Development. Cell Stem Cell. 2019 Oct 3;25(4):558-569.e7. doi: 10.1016/ j.stem.2019.08.002. Aug 29, 2019. 

https://pubmed.ncbi.nlm.nih.gov/31474560/

https://www.cell.com/cell-stem-cell/fulltext/S1934-5909(19)30337-6

# gst: global dust storms from waves in thin air.

<< Mars has a very thin atmosphere, with nearly one hundredth the density of ours on Earth, and gravity pulls with little more than one third of the strength we feel on our planet. As a result, dust storms can go global. >>

Waves in thin air with broad effects. Instituto de Astrofísica e Ciencias do Espaco. Mar 17, 2020.

https://m.phys.org/news/2020-03-thin-air-broad-effects.html

G.Gilli,  F.Forget, et al. Impact of Gravity Waves on the Middle Atmosphere of Mars: A Non‐Orographic Gravity Wave Parameterization Based on Global Climate Modeling and MCS Observations. Journal of Geophysical Research: Planets. Volume 125, Issue 3.  doi: 10.1029/2018JE005873. Feb 7, 2020.

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2018JE005873

# gst: dynamics and interactions of multiple bright droplets and bubbles, and interactions of kinks with droplets and with antikinks.

<< Droplets bearing different chemical potentials experience mass-exchange phenomena. Individual bubbles exhibit core expansion and mutual attraction prior to their destabilization. Droplets interacting with kinks are absorbed by them, a process accompanied by the emission of dispersive shock waves and gray solitons. Kink-antikink interactions are repulsive, generating counter-propagating shock waves. >> 

 

G. C. Katsimiga, S. I. Mistakidis, et al. Interactions and dynamics of one-dimensional droplets, bubbles and kinks. arXiv: 2306.07055v2 [cond-mat.quant-gas]. Jul 26, 2023.

https://arxiv.org/abs/2306.07055

Also: drop, bubble, waves, soliton, in https://www.inkgmr.net/kwrds.html

Keywords: gst, drop, bubble, kink, wave, soliton, homoclinic orbits

# s-gst: surface waves as a Turing machine

<< A droplet bouncing and wandering across a liquid surface can produce waves that store the history of its chaotic motion >>

Philip  Ball. Focus:  Surface  Waves  Store  Bouncing Droplet’s  History. Physics  9,  101. August  26,  2016.

http://physics.aps.org/articles/v9/101

S. Perrard, E. Fort, Y. Couder. Wave-Based Turing Machine: Time Reversal and Information Erasing. Phys. Rev. Lett. 117, 094502 – DOI: 10.1103/PhysRevLett.117.094502 Published 26 August 2016

http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.117.094502

# gst: apropos of collisions of a vortex dipoles, vortex unbinding, vortex pinning to the edge, and emission of rarefaction pulses.

<< Vortices and dark solitons are fundamental defects that appear in nonlinear physics at all scales, from nonlinear optics to cosmic fluids. In two or three dimensions, dark solitons are fundamentally connected to highly ordered vortex states through an intrinsic modulation instability in the surrounding matter. >>️

<< Here, [AA] report an experimental realization of ring dark soliton (RDS)  generation in a two-dimensional atomic superfluid trapped in a circular box. By quenching the confining box potential, [they] observe an RDS emitted from the edge and its peculiar signature in the radial motion. As an RDS evolves, [they] observe transverse modulations at discrete azimuthal angles, which clearly result in a patterned formation of a circular vortex dipole array. Through collisions of the vortex dipoles with the box trap, [they] observe vortex unbinding, vortex pinning to the edge, and emission of rarefaction pulses. >>

Hikaru Tamura, Cheng-An Chen, Chen-Lung Hung. Observation of Self-Patterned Defect Formation in Atomic Superfluids–from Ring Dark Solitons to Vortex Dipole Necklaces. Phys. Rev. X 13, 031029. Sep 14, 2023. 

https://journals.aps.org/prx/abstract/10.1103/PhysRevX.13.031029

Also: soliton, vortex, turbulence, waves, in: https://www.inkgmr.net/kwrds.html  

Keywords: gst, soliton, dark soliton, vortex, turbulence, waves. 

# astro: the binary black hole spin distribution, a sort of cosmic estension of Mr. Jelly Roll

<< The direct detection of gravitational waves from merging binary black holes opens up a window into the environments in which binary black holes form. One signature of such environments is the angular distribution of the black hole spins >>

AA << report that, if the magnitudes of the black hole spins are allowed to extend to high values, the effective spins for these systems indicate a 0.015 odds ratio against an aligned angular distribution compared to an isotropic one [isotropic spin orientation: the spins of the black holes are randomly oriented with respect to the orbit of the binary system]. When considering the effect of ten additional detections, this odds ratio decreases to 2.9 × 10−7 against alignment >>

Will M. Farr, Simon Stevenson, et al. Distinguishing spin-aligned and isotropic black hole populations with gravitational waves. Nature 548, 426–429 Aug 24, 2017 doi: 10.1038/nature23453

http://www.nature.com/nature/journal/v548/n7668/full/nature23453.html

https://arxiv.org/abs/1706.01385

<< Amico, qualunque  cosa suonerai . . . suonerai Jelly Roll >>

Jelly Roll Morton (opp. Mouton, alias di Ferdinand La Menthe, opp. La Mothe, New Orleans, 20 ott ~1885 - Los Angeles, 10 luglio 1941, ~56a).  Ref: Alan Lomax. "Mister Jelly Roll". Duell, Sloan & Pearce, New York (1950);  cit. in: Arrigo Polillo, "JAZZ". Oscar Saggi Mondadori. (1977):315,325.

http://inkpi.blogspot.it/search?q=jelly+roll

# gst: random walk model for dual cascades in wave turbulence.

<< Dual cascades in turbulent systems with two conserved quadratic quantities famously arise in both two-dimensional hydrodynamic turbulence and also in wave turbulence based on four-wave interactions. >>

<< in wave turbulence the systematic spectral fluxes observed in a dual cascade do not require an irreversible dynamical mechanism, rather, they arise as the inevitable outcome of blind chance. >>️️

Oliver Bühler. Random walk model for dual cascades in wave turbulence. Phys. Rev. E 109, 055102. May 1, 2024. 

https://journals.aps.org/pre/abstract/10.1103/PhysRevE.109.055102

Also: waves, turbulence, random, weak, in https://www.inkgmr.net/kwrds.html 

Keywords: gst, waves, turbulence, weak turbulence, random, random walks

# gst: tiny deviations (inside a phase transition) to avoid a near-complete annihilation.

<< Recently discovered ripples of spacetime called gravitational waves could contain evidence to prove the theory that life survived the Big Bang because of a phase transition that allowed neutrino particles to reshuffle matter and anti-matter, >>

<< According to the Big Bang theory of modern cosmology, matter was created with an equal amount of anti-matter. If it had stayed that way, matter and anti-matter should have eventually met and annihilated one to one, leading up to a complete annihilation.

But our existence contradicts this theory. To overcome a complete annihilation, the Universe must have turned a small amount of anti-matter into matter creating an imbalance between them. >>  

<< the Universe went through a phase transition so that neutrinos could reshuffle matter and anti-matter. >>

Showing how the tiniest particles in our Universe saved us from complete annihilation. Kavli Institute for the Physics and Mathematics of the Universe. Feb 3, 2020.

https://m.phys.org/news/2020-02-tiniest-particles-universe-annihilation.html

Jeff A. Dror, Takashi Hiramatsu, et al.  Testing the Seesaw Mechanism and Leptogenesis with Gravitational Waves.  Phys. Rev. Lett. 124, 041804. doi: 10.1103/PhysRevLett.124.041804. Jan 28, 2020. 

https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.124.041804

# gst: apropos of apparent erratic dynamics, the self-organization of drops bouncing on a vertically-vibrated surface

<< A drop bouncing on a vertically-vibrated surface may self-propel forward by Faraday waves and travels along a fluid interface. >>

<< A fine anal­ysis of the pairwise density function shows that while being dynamic, time-evolving and presenting many in­dications of a good mixing in the phase space, the sys­tem adopts in average preferred distances which origin has been rationalized by analysing the internal symme­try of the waves. Thus (AA) have shed light numerically on a statistical many-body wave self-organisation in an apparent erratic dynamics. >>

Adrien Hélias, Matthieu Labousse. Statistical self-organization of walking drops. arXiv:2201.07689v1 [cond-mat.soft]. Jan 19, 2022.

https://arxiv.org/abs/2201.07689

Also

keyword 'drop' | 'droplet' in FonT

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

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

keyword 'goccia' in Notes (quasi-stochastic poetry): 

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

keywords: gst, drops, self-organization, erratic dynamics, erraticity

# gst: early seismic waves could allow to glimpse the power of the main temblor

AA << explore databases of earthquake source time functions and find that they are composed of distinct peaks that (..) call subevents (..) the main event magnitude can be estimated after observing only the first few subevents. >>

Philippe Danre, Jiuxun Yin, et al. Earthquakes Within Earthquakes: Patterns in Rupture Complexity. Geophysical Research Letters. Volume 46, Issue 13. doi: 10.1029/ 2019GL083093. Jun 25, 2019.   https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2019GL083093

Anna Fiorentino. Early seismic waves hold the clue to the power of the main temblor. Harvard University. Aug 8, 2019.  https://m.phys.org/news/2019-08-early-seismic-clue-power-main.html