# 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

# astro: black holes (as Q-ball-type saturons) could admit multi-vortex dynamics

<< Theoretical physicists argue that black holes admit vortex structures >>

Img << Sketch of a black hole endowed with multiple vortices. Colors denote the orientation, with the associated trapped magnetic field lines in black. Credit: Dvali et al. >>️

<< Recently, a new quantum framework for black holes, namely in terms of Bose-Einstein condensates of gravitons (the quanta of gravity itself), has been introduced, (..) Up until our article was published, rotating black holes have not been thoroughly studied within this framework. However, they might not only exist, but also be the rule rather than the exception. >> Florian Kühnel. 

️

Ingrid Fadelli. Theoretical physicists argue that black holes admit vortex structures. Phys.org. Sep 09, 2022. 

https://phys.org/news/2022-09-theoretical-physicists-black-holes-vortex.html

AA << argue that black holes admit vortex structure. This is based both on a graviton-condensate description of a black hole as well as on a correspondence between black holes and generic objects with maximal entropy compatible with unitarity, so-called saturons. (They) show that due to vorticity, a Q-ball-type saturon of a calculable renormalizable theory obeys the same extremality bound on the spin as the black hole. Correspondingly, a black hole with extremal spin emerges as a graviton condensate with vorticity. (..) Next, (AA) show that in the presence of mobile charges, the global vortex traps a magnetic flux of the gauge field. This can have macroscopically observable consequences. >>

️

Gia Dvali, Florian Kuhnel, Michael Zantedeschi. Vortices in Black Holes. Phys. Rev. Lett. 129, 061302. Aug 3, 2022.  

https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.129.061302

Also

keyword 'black hole' in FonT  

https://flashontrack.blogspot.com/search?q=black+hole

Keywords: astro, astrophysics, black hole, rotating black hole, vortex, vorticity

# gst: solitons as 'emergent elastic objects with spatially dependent stiffness'

<< Since the 1950s, topological solitons have been used to describe elementary particles and particle-like field configurations that appear in systems ranging from subatomic to cosmological scales. Particles are topologically protected, for which transitions to states with different topological charges are restricted. However, formation and annihilation of solitons are universal in almost all branches of physics, which implies that topological protection collapses at certain condition unrevealed. >>

<< Here, (AA) show that solitons can be regarded as emergent elastic objects with spatially dependent stiffness, and a second-order topological phase transition initiates at its softened points, i.e., points with a vanishing eigenvalue of the emergent stiffness matrix. >>

️

Yangfan Hu. Emergent elasticity and topological stability of solitons. arXiv: 2208.14916v1 [nlin.PS]. Aug 31, 2022. 

https://arxiv.org/abs/2208.14916

Also

'Second-order phase transitions' 

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

keyword 'solitons' in FonT

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

Keywords: gst, solitons, transition, phase_transition

# gst: "birds of a feather flock together", the swarmalators

<< Swarmalators have emerged as a new paradigm for dynamical collective behavior of multi-agent systems due to the interplay of synchronization and swarming that they inherently incorporate. Their dynamics have been explored with different coupling topologies, interaction functions, external forcing, noise, competitive interactions, and from other important viewpoints. Here (AA) take a systematic approach and review the collective dynamics of swarmalators analytically and/or numerically. Long-term states of position aggregation and phase synchronization are revealed in this perspective with some future >>️

Gourab Kumar Sar, Dibakar Ghosh. Dynamics of swarmalators: A pedagogical review. arXiv: 2208.14803v1 [nlin.AO]. Jul 25, 2022. Europhysics Letters 139, 53001. 

doi: 10.1209/ 0295-5075/ac8445. 

https://arxiv.org/abs/2208.14803

Also

Keyword 'swarm' in FonT

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

Keywords: gst, behavior, collective behavior, self-organization, synchronization, spontaneous synchronization, swarm, swarmalators.

# gst: a backflipping behavior of air bubbles when they collide with a tilted surface

AA << observe that air bubbles exhibit a backflipping behavior when they collide with a tilted surface. >>

<< Particle image velocimetry reveals that the backflipping behavior is caused by wake-induced circulation around the bubble, which applies a lift force on the bubble. >>

<< The theoretical results are in good agreement with the experiments confirming the key role of the wake-induced lift force in backflipping. >>

Alireza Hooshanginejad, Anuj Baskota, Sunghwan Jung. Backflipping motion of air bubbles colliding with a tilted wall. arXiv: 2208.14486v1 [physics.flu-dyn]. Aug 30, 2022.

https://arxiv.org/abs/2208.14486 

️

Also

keyword "bubble" in FonT

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

keyword "bolla" | "bolle" in Notes (quasistochastic-poetry)

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

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

Keywords: gst, bubble, behavior, backflipping behavior, oblique collisions

# behav: cry / not cry, babe ... POMC neurons modulate the crying behavior of pups (among mice)

<< Infants cry when separated from their mothers. Here, (AA) show that POMC (pro-opiomelanocortin) neurons in the arcuate nucleus of the hypothalamus—via ß-endorphin production and signaling—modulate the crying behavior of mouse pups. The effect of POMC neurons on vocal behavior depends on the expression of µ-opioid receptors, the main receptor for ß-endorphin. Thus, POMC neurons in the hypothalamus modulate infant cry through opioid signaling. >>️

Gabriela M. Bosque Ortiz, Marcelo O. Dietrich. POMC neurons modulate infant vocalizations through opioid signaling. bioRxiv 2022.08.15.504046. 

doi: 10.1101/ 2022.08.15.504046. Aug 15, 2022. 

https://www.biorxiv.org/content/10.1101/2022.08.15.504046v1

Also

keywords 'behav' in FonT

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

keyword 'pnei' in FonT

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

keyword 'pnei' in Notes 

(quasi-stochastic poetry)

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

Keywords: behav, brain, pnei, opioid signaling

# gst: apropos of vibrating pivots, driving a damped coplanar double pendulum.

AA << present results of linear and nonlinear motions of a parametrically driven coplanar double pendulum with velocity-dependent damping. The equations of motion of a damped double pendulum of unequal masses with its pivot vibrated vertically are different from those obtained under gravity modulation. 

Linear stability analysis shows that tongue-shaped marginal stability curves divide the plane of driving parameters into multiple regions of subharmonic and harmonic instabilities. The instability zones for one normal mode overlap with those for the other. 

The double pendulum may oscillate or rotate about its pivot harmonically or subharmonically. The limit cycles corresponding to the normal mode oscillations of a double pendulum of equal masses are squeezed into a line in its configuration space. 

For unequal masses, two marginal curves for subharmonic instabilities merge to form a double-well shaped curve in the presence of damping, which is qualitatively new. The pendulum shows driving amplitude sensitive multi-period complex oscillations for driving parameters near the extrema of the merged instability zones and boundaries of the overlapping zones. 

For larger driving amplitude, the pendulum shows subharmonic, harmonic or chaotic rotations. >>

️

Rebeka Sarkar, Krishna Kumar, Sugata Pratik Khastgir. Parametrically driven damped coplanar double pendulum. arXiv:2208.03292v1 [physics.class-ph]. Aug 2, 2022. 

https://arxiv.org/abs/2208.03292

Also

keyword 'pendulum' in FonT

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

keyword 'pendolo' | 'pendola' in Notes

(quasi-stochastic poetry)

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

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

Keywords: gst, pendulum, double pendulum, instability, chaos, chaotic rotations