# astro: eight new echoing black hole binaries (in Milky Way)

<< Scattered across our Milky Way galaxy are tens of millions of black holes—immensely strong gravitational wells of spacetime, from which infalling matter, and even light, can never escape. Black holes are dark by definition, except on the rare occasions when they feed. As a black hole pulls in gas and dust from an orbiting star, it can give off spectacular bursts of X-ray light that bounce and echo off the inspiraling gas, briefly illuminating a black hole's extreme surroundings. >>

<< In a study appearing (..) in the The Astrophysical Journal, (AA) report (..) eight new echoing black hole binaries in our galaxy. Previously, only two such systems in the Milky Way were known to emit X-ray echoes. >>️

 << Kara (Erin Kara) and her colleagues are using X-ray echoes to map a black hole's vicinity, much the way that bats use sound echoes to navigate their surroundings. (..)  As a side project, Kara is working with MIT education and music scholars, Kyle Keane and Ian Condry, to convert the emission from a typical X-ray echo into audible sound waves. >>️️

Jennifer Chu. Search reveals eight new sources of black hole echoes. MIT.  May 2, 2022. 

https://phys.org/news/2022-05-reveals-sources-black-hole-echoes.html

https://youtu.be/iIeIag2Ji8k

Jingyi Wang, Erin Kara, et al. The NICER "Reverberation Machine": A Systematic Study of Time Lags in Black Hole X-Ray Binaries. ApJ. 930, 18. May 2, 2022. 

https://iopscience.iop.org/article/10.3847/1538-4357/ac6262

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keyword 'black hole' in FonT

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keyword 'waves' in FonT

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keyword 'onda' in Notes 

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Keywords: astro, black hole, echoes, waves

# gst: non-trivial behaviors of a rotating (physical) double pendulum

<< The double pendulum, a simple system of classical mechanics, is widely studied as an example of, and testbed for, chaotic dynamics. In 2016, Maiti et al. studied a generalization of the simple double pendulum with equal point-masses at equal lengths, to a rotating double pendulum, fixed to a coordinate system uniformly rotating about the vertical. In this paper, (AA) study a considerable generalization of the double pendulum, constructed from physical pendula, and ask what equilibrium configurations exist for the system across a comparatively large parameter space, as well as what bifurcations occur in those equilibria. >>️

<< the non-trivial bifurcation (AA) have found (..), may actually be rightly understood as three additional bifurcations: there is a narrow region, approximately the ‘crease’ of the surface in Fig. 5, within which a vertical line (..) intersects the surface three times; (..). Thus three non-trival bifurcations would be expected in the corresponding bifurcations plots. >>️

Jonathan Tot, Robert H. Lewis. On the Equilibria and Bifurcations of a Rotating Double Pendulum. arXiv:2204.12437v2 [math.DS]. May 7, 2022. 

https://arxiv.org/abs/2204.12437

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keyword 'pendulum' in FonT

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keyword 'pendolo' | 'pendola' in Notes

(quasi-stochastic poetry)

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Keywords: gst, pendulum, double pendulum, behavior, chaos 

# gst: even tight-binding billiards could exhibit chaotic behaviors

<< Recent works have established universal entanglement properties and demonstrated validity of single-particle eigenstate thermalization in quantum-chaotic quadratic Hamiltonians. However, a common property of all quantum-chaotic quadratic Hamiltonians studied in this context so far is the presence of random terms that act as a source of disorder. >>

AA << introduce tight-binding billiards in two dimensions, which are described by non-interacting spinless fermions on a disorder-free square lattice subject to curved open boundaries. >>

They <<  show that many properties of tight-binding billiards match those of quantum-chaotic quadratic Hamiltonians (..) these properties indeed appear to be consistent with the emergence of quantum chaos in tight-binding billiards. This statement nevertheless needs to be taken with some care since there exist a sub-extensive (in lattice volume) set of single-particle eigenstates that are degenerate in the middle of the spectrum at zero energy (i.e., zero modes), for which the agreement with RMT (random matrix theory) predictions may not be established. >>

Iris Ulcakar, Lev Vidmar. Tight-binding billiards. arXiv:2206.07078v1 [cond-mat.stat-mech]. Jun 14, 2022. 

https://arxiv.org/abs/2206.07078

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keyword 'chaos' | 'chaotic' in Font

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keyword 'caos' | 'caotico' in Notes (quasi-stochastic poetry)

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keywords: gst, billiard, chaos, chaotic behavior

# life: sull'esportabile funky

<< E conficca nel perpetuato dall'acre stagnola //

- cauto pei prevedibili ritorni in semicroma - //

l'acustica fluida porfina che percola //

casuali pulsatili a sonda sulle tronche foniche //

d' arso d'achenio // >>

Sull'esportabile funky. Notes. Jan 25, 2006.

https://inkpi.blogspot.com/2006/01/1948-sull-esportabile-funky.html  

"Directions".  Miles Davis. "The Cellar Door Session 1970" CD6. Sony. (2005).

https://en.m.wikipedia.org/wiki/The_Cellar_Door_Sessions_1970

porfina: https://www.treccani.it/enciclopedia/porfina

achenio: https://www.treccani.it/enciclopedia/achenio

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# gst: switch to three players within the Parrondo game

<< Parrondo's paradox indicates a paradoxical situation in which a winning expectation may occur in sequences of losing games. There are many versions of the original Parrondo's games in the literature, but the games are played by two players in all of them. (AA) introduce a new extended version of games played by three players and a three-sided biased dice instead of two players and a biased coin in this work.  >>️

<< Figure 11 shows the result of combination switches A and B for the fair probabilities in set S_5. The simulation results are performed so on until 100 steps were done, and each step is averaged over 10000 repeats. This strategy, different from the others and even the original Parrondo's paradox, produces a fair expectation from two noisy switches in which the combination of two fair switches is fair. >>

️

Atiyeh Fotoohinasab. A new generalization of Parrondo's games to three players and its application in genetic switches.  arXiv: 2101.11401v2 [q-bio.PE]. Feb 2, 2021. 

https://arxiv.org/abs/2101.11401 

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Keywords: gst, games, parrondo, three-body

# pnei: brain motor and fear circuits regulate leukocytes during acute stress

<< The nervous and immune systems are intricately linked. Although psychological stress is known to modulate immune function, mechanistic pathways linking stress networks in the brain to peripheral leukocytes remain poorly understood. Here, (AA) show that distinct brain regions shape leukocyte distribution and function throughout the body during acute stress in mice. >>️

Poller, W.C., Downey, J., et al. Brain motor and fear circuits regulate leukocytes during acute stress. Nature. doi: 10.1038/ s41586-022-04890-z. May 30, 2022. 

https://www.nature.com/articles/s41586-022-04890-z

PNEI: Psycho-Neuro-Endocrine-Immunology  

https://pubmed.ncbi.nlm.nih.gov/?term=pnei

Also

Inchingolo G. Percezione dello stato di salute e leucociti in anziani ultraottantenni.   Atti 36 Congresso Nazionale Società Italiana di Gerontologia e Geriatria, Palermo, 7-10 Novembre 1991.   Giornale di Gerontologia 1991; XXXIX(11): 753.

https://sites.google.com/site/inkgmr2/papers

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Keywords: pnei, neuroimmunology, leukocytes, fear, stress, virus, viral infection, adaptation, adaptive immunity 

# gst: intentional defects to trap confined acoustic modes that are protected from perturbation

AA << has discovered how to exploit certain defects to protect confined energy in acoustics systems. Their experimental approach provides a versatile platform to create at-will defects for further theoretical validation and to improve control of waves in other systems, such as light >>

<< We set to understand whether topological defects, such as disclinations, can be created to trap highly confined acoustic modes that are protected from perturbation, (..) Our core insight was that, if we consider the point group symmetry of the disclination, a pair of disclinations modes are prevented from pairing away from zero frequency. This protection mechanism results from the interplay of the symmetry-protected topological phase of the crystalline lattice and the topological charge and symmetry of the disclination. >> Wladimir A. Benalcazar.

<< This is the first work experimentally validating that such protected states exist in the disclination core, >> Yun Jing. 

️

Ashley J. Wennersherron. Researchers find imperfections provide protection for system symmetry. Penn State College of Engineering. May 20, 2022.

https://phys.org/news/2022-05-imperfections-symmetry.html

Sarah Wells. Symmetrical Binding for Topological States. Physics 15, s56. Apr 26, 2022. 

https://physics.aps.org/articles/v15/s56

Yuanchen Deng, Wladimir A. Benalcazar, et al. Observation of Degenerate Zero-Energy Topological States at Disclinations in an Acoustic Lattice. Phys. Rev. Lett. 128, 174301. Apr 26, 2022. 

https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.128.174301

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Keywords: gst, acoustics, acoustic metamaterials, symmetry, system symmetry, imperfection, defect, topological defects, disclination