# gst: phase transition of inertial self-propelled agents, a ‘inverse modeling’ approach.

AA << formulate and analyze a kinetic MFG (Mean-field Game) model for an interacting system of non-cooperative motile agents with inertial dynamics and finite-range interactions, where each agent is minimizing a biologically inspired cost function. >>️️

The << ‘inverse modelling’ approach is to stipulate that the collective behavior of a population of decision-making agents is a solution to a collective optimization or optimal control problem. (..) In a MFG system, the collective behavior is the result of each agent solving an optimal control problem that depends on its own state and control as well as the collective state. MFGs formulated in continuous state space and time are described by coupled set of forward-backward in time nonlinear partial differential equations (PDEs). >>

<< While standard kinetic or hydrodynamic equations used for modelling collective behavior are initial value problems (IVP or evolution PDEs), the MFG systems have a forward-backward in time structure, and hence consist of boundary value problem (BVP in time PDEs). >>

<< By analyzing the associated coupled forward-backward in time system of nonlinear Fokker-Planck and Hamilton-Jacobi-Bellman equations, (AA) obtain conditions for closed-loop linear stability of the spatially homogeneous MFG equilibrium that corresponds to an ordered state with non-zero mean speed. Using a combination of analysis and numerical simulations, (AA) show that when energetic cost of control is reduced below a critical value, this equilibrium loses stability, and the system transitions to a traveling wave solution. >>️

️

Piyush Grover, Mandy Huo. Phase transition in a kinetic mean-field game model of inertial self-propelled agents. arXiv: 2407.18400v1 [math.OC]. Jul 25, 2024. 

https://arxiv.org/abs/2407.18400

Also: transition, wave, game, in https://www.inkgmr.net/kwrds.html 

Keywords: gst, transition, criticality, bifurcations, wave, games

# brain: arterial pressure pulsations could modulate neuronal activity.

<< Spontaneous slow oscillations have been described in the rat olfactory bulb local field potential, even in the absence of respiration. What is the origin of these oscillations? >>

AA << discovered a subpopulation of neurons within the olfactory bulb that can directly sense cardiovascular pressure pulsations (..). The modulation of their excitability is transduced by mechanosensitive ion channels. >>

<< Thus, there exists a fast pathway for the interoception of heartbeat whereby arterial pressure pulsations within the brain modulate neuronal activity. >> Peter Stern. ️

Luna Jammal Salameh, Sebastian H. Bitzenhofer, et al. Blood pressure pulsations modulate central neuronal activity via mechanosensitive ion channels. Science. Vol 383, Issue 6682. Feb 2, 2024. 

https://www.science.org/doi/10.1126/science.adk8511

img: https://www.science.org/cms/10.1126/science.adk8511/asset/76a1eaf8-61d3-4233-bc2a-be2276f367cd/assets/images/large/science.adk8511-fa.jpg

Also: brain, pnei, soliton, in https://www.inkgmr.net/kwrds.html  

Keywords: brain, pnei, olfactory bulb, spontaneous slow oscillations, wave, soliton

# 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

# gst: mitigate | eliminate side lobes from superoscillatory waves (to manipulate nanoparticles)

<< A sharp-edged aperture is a promising solution for eliminating side lobes from superoscillatory waves. >>

<< Optical superoscillation refers to a wave packet that can oscillate locally in a frequency exceeding its highest Fourier component. This intriguing phenomenon enables production of extremely localized waves that can break the optical diffraction barrier. >>

<< The trouble is that strong side lobes accompany the main lobes of superoscillatory waves, which limits the field of view and hinders application. >>️

<< A central microdisc with cylindrical diffraction gives rise to a superoscillatory light spot of a size within the optical diffraction limit. A pair of sharp-edged apertures ensures constructive interference with the high-spatial-frequency waves. That interference effectively eliminates side lobes along a symmetric cut that can be adjusted in the transverse plane by rotating the moonlike apertures. >>

️

<< the cylindrical diffraction of the central microdisc produces superoscillatory waves with Bessel-like forms. These forms enable the delicate structures of the superoscillatory waves propagating in free space to travel much farther than the evanescent light waves. (..) this intriguing propagation effect of superoscillation holds promise for potential application in nanoparticle manipulation, as well as superresolution imaging. >>️

️

Optical superoscillation without side waves. SPIE-International Society for Optics and Photonics. Jun 24, 2021.

https://www.sciencedaily.com/releases/2021/06/210624170837.htm

Yanwen Hu, Shiwang Wang, et al. Optical superoscillatory waves without side lobes along a symmetric cut. Advanced Photonics, 3(4), 045002 doi: 10.1117/ 1.AP.3.4.045002. Jun 23, 2021. 

https://www.spiedigitallibrary.org/journals/advanced-photonics/volume-3/issue-4/045002/Optical-superoscillatory-waves-without-side-lobes-along-a-symmetric-cut/10.1117/1.AP.3.4.045002.full

# gst; apropos of hair that can be combed, some perturbation fields, along the event horizon of extreme black holes, seem to evolve in time indefinitely

 <<  black holes can be fully characterized by only three physical quantities: their mass, spin and charge. Since they have no additional "hairy" attributes to distinguish them, black holes are said to have "no hair"—Black holes of the same mass, spin, and charge are exactly identical to each other. >> 

AA << discovered that a special kind of black hole violates black hole uniqueness, the so-called "no hair" theorem. Specifically, the team studied extremal black holes—holes that are "saturated" with the maximum charge or spin they can possibly carry. They found that there is a quantity that can be constructed from the spacetime curvature at the black hole horizon that is conserved, and measurable by a distant observer. Since this quantity depends on how the black hole was formed, and not just on the three classical attributes, it violates black hole uniqueness. This quantity constitutes "gravitational hair" and potentially measurable by recent and upcoming gravitational wave observatories like LIGO and LISA. >>

<< even though external perturbations of extreme black holes decay as they do also for regular black holes, along the event horizon certain perturbation fields evolve in time indefinitely. >>

<< The uniqueness theorems assume time independence. But the Aretakis phenomenon explicitly violates time independence along the event horizon. This is the loophole through which the hair can pop out and be combed at a great distance by a gravitational wave observatory, >> Lior Burko.

Extreme black holes have hair that can be combed. Theiss Research. Jan 26, 2021.

https://phys.org/news/2021-01-extreme-black-holes-hair.html

Lior M. Burko, Gaurav Khanna, Subir Sabharwal. Scalar and gravitational hair for extreme Kerr black holes. Phys. Rev. D 103, L021502. Jan 26, 2021.

https://journals.aps.org/prd/abstract/10.1103/PhysRevD.103.L021502  

# gst: apropos of waves perturbed by weak turbulences

<< Wave phenomena are ubiquitous at all scales throughout the Universe, and where there are waves, there’s the potential for wave turbulence. Wave turbulence is the physical state that arises in a continuous medium when a large number of wave modes interact with each other randomly. >>

<< A specific case of wave turbulence in which weakly nonlinear waves propagate in an unbounded space is described by weak turbulence theory. Capturing the dynamics of this regime will be helpful to accurately model large fluid systems. >>

<< In a rotating fluid, the predicted wave spectrum for interacting weakly nonlinear inertial waves is perturbed by the formation of geostrophic modes—columnar vortices aligned with the rotation axis (..) (AA) successfully suppress geostrophic modes with the addition of two honeycomb-patterned plates, allowing them to confirm the predictions of weak turbulence theory. >>

Sergey Nazarenko. Verifying Weak Turbulence Theory.  Physics 13, 194. Dec 14, 2020. 

https://physics.aps.org/articles/v13/194

Eduardo Monsalve, Maxime Brunet, et al. Quantitative Experimental Observation of Weak Inertial-Wave Turbulence. Phys. Rev. Lett. 125, 254502. Dec 14, 2020.

https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.125.254502

# life: oops! aprops of tsunami wave hazards, exposure to other 'Fukushima Daiichi Nuclear Power Plant' accidents appear to exist ...

<< A major tsunami in the northern Arabian Sea could severely impact the coastlines of India and Pakistan, which are studded with sensitive installations including several nuclear plants, >>

<< Atomic power stations functioning along the Arabian Sea include Tarapur (1,400 megawatts) in India's Maharashtra state, Kaiga (being expanded to 2,200 megawatts) in Karnataka state and Karachi in Pakistan (also being expanded to 2,200 megawatts). A mega nuclear power plant coming up at Jaitapur, Maharashtra will generate 9,900 megawatts, while another project at Mithi Virdi in Gujarat may be shelved because of public opposition. >>

<< Nuclear power plants are located along coasts because their enormous cooling needs can be taken care of easily and cheaply by making using abundant seawater. >>

Nuclear plants in Arabian Sea face tsunami risk. SciDev.Net. Sep 21, 2020.

https://phys.org/news/2020-09-nuclear-arabian-sea-tsunami.html

Rajendran, C.P., Heidarzadeh, et al. The Orphan Tsunami of 1524 on the Konkan Coast, Western India, and Its Implications. Pure Appl. Geophys. doi: 10.1007/ s00024-020-02575-0. Sep 7, 2020. 

https://link.springer.com/article/10.1007/s00024-020-02575-0

<< The earthquake had also generated a 14 m high tsunami that arrived shortly afterwards and swept over the plant's seawall and then flooded the lower parts of reactors 1–4. This caused the failure of the emergency generators and loss of power to the circulating pumps.(..) The resultant loss of reactor core cooling led to three nuclear meltdowns, three hydrogen explosions, and the release of radioactive contamination in Units 1, 2 and 3 between 12 and 15 March. >>

Fukushima Daiichi nuclear disaster.  Last edited Sep 25, 2020 by Dougsim.

https://en.m.wikipedia.org/wiki/Fukushima_Daiichi_nuclear_disaster

Also

2157 - il pino di takata matsubara. Notes. Apr 01, 2011. (quasi-stochastic poetry)

https://inkpi.blogspot.com/2011/04/2157-il-pino-di-takata-matsubara.html

Also

keyword 'onda' in Notes (quasi-stochastic poetry)

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

Also

keyword 'wave' in Font

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

# gst: contactless manipulation of droplets levitating in an acoustic wave

<< A unique, versatile, and material-independent approach to manipulate contactlessly and merge two chemically distinct droplets suspended in an acoustic levitator is reported. Large-amplitude axial oscillations are induced in the top droplet by low-frequency amplitude modulation of the ultrasonic carrier wave, which causes the top sample to merge with the sample in the pressure minimum below. The levitator is enclosed within a pressure-compatible process chamber to enable control of the environmental conditions. The merging technique permits precise control of the substances affecting the chemical reactions, the sample temperature, the volumes of the liquid reactants down to the picoliter range, and the mixing locations in space and time. >>

Stephen J. Brotton, Ralf I. Kaiser. 

Controlled Chemistry via Contactless Manipulation and Merging of Droplets in an Acoustic Levitator. Anal. Chem. 2020, 92, 12, 8371–8377. doi: 10.1021/ acs.analchem.0c00929. Jun 1, 2020. 

https://pubs.acs.org/doi/10.1021/acs.analchem.0c00929#

Levitating droplets allow scientists to perform 'touchless' chemical reactions.  American Chemical Society. Jun 24, 2020.

https://phys.org/news/2020-06-levitating-droplets-scientists-touchless-chemical.html