# gst: on the geometry of spreading puddles.

<< ️(AA) develop a geometric model for the spreading of shallow, viscous puddles of arbitrary shape, building on the recent 'capillary current' model for axisymmetric droplets. In short, (They) assume that a spreading puddle remains close to instantaneous mechanical equilibrium as it spreads, with hydrostatic pressure balanced by surface curvature. In turn, its contact line advances so as to maximize the rate of energy loss subject to viscous dissipation. >>

<< ️The resulting system yields a natural geometric evolution equation for both the two-dimensional footprint and the three-dimensional depth profile of a spreading puddle. In appropriate limits, it recovers the classical spreading laws for axisymmetric droplets, a local version of the Hoffman-Voinov-Tanner law for small non-axisymmetric puddles, and a nonlocal Hele-Shaw-like description for large, relatively regular puddles. >>

David Darrow. On the Geometry of Spreading Puddles. arXiv: 2606.13893v1 [physics.flu-dyn]. Jun 11, 2026.

https://arxiv.org/abs/2606.13893

Also: drop, droplet, droploid, in https://www.inkgmr.net/kwrds.html 

Keywords: gst, drops, droplets, droploids, spreading puddle, axisymmetric droplets, surface curvature, viscous dissipation.

# gst: dissipation-coherence tradeoff for stochastic oscillations.

<< ️Autonomous noisy oscillations in biochemical and mesoscopic systems require nonequilibrium driving and therefore dissipation. A striking conjecture by Oberreiter, Barato, and Seifert (OBS) proposes a universal lower bound on the entropy produced per oscillation period in terms of the coherence number of the slowest oscillatory mode (L. Oberreiter et al. [Phys. Rev. E 106, 014106 (2022)]). >>

<< ️Here (AA) derive a weaker but rigorous lower bound that preserves the OBS structure while introducing a mode-uniformity factor that quantifies how evenly the oscillatory eigenmode is distributed across states in the steady-state inner product. The result makes explicit that an eigenvalue-only prefactor can fail when the dominant oscillatory mode is localized. >>

<< ️(They) also outline a proof-of-principle route for estimating this factor from low-dimensional data under single-mode dominance and sufficiently informative measurements, and derive an eigenvector-free corollary using only the smallest stationary probability. >>

<< ️Translation-invariant Markov jump processes on a ring provide a symmetry-protected class with 𝜂=1, so the refinement reduces to the OBS form; the drift-diffusion limit on a circle saturates the bound. >>

Jie Gu. Dissipation-coherence tradeoff for stochastic oscillations. Phys. Rev. E 113, 064130.  Jun 15, 2026.

https://journals.aps.org/pre/abstract/10.1103/zxw1-zdb7

arXiv: 2606.05498v1 [cond-mat.stat-mech]. Jun 3, 2026.

https://arxiv.org/abs/2606.05498

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

Keywords: gst, noise, disorder, dissipation, entropy, stochasticity, stochastic processes, autonomous noisy oscillations, stochastic oscillations, disorder-induced localization, time series analysis, transitions.

# life: apropos of singular, bizarre, un.expected convergences, here an asymptotic, extreme, double 'quasistochastic tit-for-tat' exploit (within the same time window).

(A1)

<< “There were no moments of friction or disagreement,” Italian Prime Minister Giorgia Meloni said at a press conference Wednesday. “I found that, overall, there was a desire to work together, and that’s not something to be taken for granted.” >>. 

Myah Ward, Clea Caulcutt, Giorgio Leali. Trump clears low bar for G7 summit in France. Jun 17, 2026.

https://www.politico.com/news/2026/06/17/trump-and-allies-keep-the-peace-at-the-g7-summit-after-months-of-tumult-00966117

(A2)

<< However, Trump has since given a phone interview with Italy's La7 TV channel in which he alleged: "She begged me to take a photo with her; I felt sorry for her." >>. 

Paul Kirby, Europe digital editor, Davide Ghiglione, Rome, James Landale, Diplomatic correspondent. Italy's Meloni says Trump 'made up' story that she 'begged' him for photo at G7. BBC. Jun 19, 2026. 

https://www.bbc.com/news/articles/c20y1ygn707o

(B) 

<< Donald Trump arrived in France yesterday for this morning’s G7

summit and promptly confirmed America’s capitulation to Iran. >>

Tom Nichols. Trump Does Not Understand the War He Lost. The Atlantic Daily. Jun 16, 2026.

https://www.theatlantic.com/newsletters/2026/06/trump-g7-comments-misunderstsand-middle-east/687569/

(A&B)

<< qui i due estremi: era modicamente non cooperatore e ha ricevuto come reazione una "bastonata"; era assolutamente ostile e ha ricevuto la classica "pacca sulla spalla" ... >>

Donald, what he can do (with less than four lines ...). FonT. May 23, 2016.

https://flashontrack.blogspot.com/2016/05/p-usa-potus-race-donald-what-he-can-do.html 

FonT

Ultimately, here too one could hypothesize another case of historic, singular checkmate of 'one against all'. Anzicheforse?

Also: Mr. Donald, tit-for-tat, game, dance, in https://www.inkgmr.net/kwrds.html

Also: here's another checkmate (FonT. Dec 4, 2024)

https://flashontrack.blogspot.com/2024/12/life-apropos-of-saliva-healers-herd.html 

Keywords: Mr. Donald, tit-for-tat, game, dance 

# gst: on maximal delay of stability loss for dynamical bifurcations.

<< ️(AA) consider a dynamical bifurcation caused by a slow passage through a static bifurcation point: in a system depending on a parameter, the parameter changes slowly in time and passes through the critical value corresponding to the loss of stability of an equilibrium via a Poincaré--Andronov--Hopf bifurcation in the frozen system. >>

<< ️If the system is analytic, then the loss of stability is inevitably delayed: phase points attracted to the equilibrium in the stability region remain near the equilibrium for a long time after entering the instability region, so that the parameter changes by an amount of order ~1 independently of how slow the variation of the parameter is. Remarkably, there exists a maximal delay: all phase points attracted to the stable equilibrium before a certain threshold value of the parameter leave a neighbourhood of the unstable equilibrium almost simultaneously near another threshold value of the parameter, known as a buffer point. >>

<< ️A delay of stability loss beyond the buffer point is impossible unless the initial data have a very special form. (AA) assume that, although the equilibrium is non-degenerate for real values of the parameter, one of its eigenvalues vanishes generically for some complex value of the parameter (a complex analogue of a saddle-node bifurcation), and that this complex singularity is, in a suitable sense, the closest one to the real Poincaré--Andronov--Hopf bifurcation point. >>

<< ️(AA) show that the value of maximal delay is determined by this complex singularity: the threshold values defining the maximal delay are the intersection points of the Stokes lines associated with this singularity and the real axis. (They) study these phenomena in the framework of slow--fast dynamical systems. >>

Anatoly Neishtadt. On Maximal Delay of Stability Loss for Dynamical 

Bifurcations. arXiv: 2606.07662v1 [math.DS]. Jun 3, 2026.

https://arxiv.org/abs/2606.07662

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

Keywords: gst, instability, transitions, dynamical bifurcation, bifurcation point, loss of stability, delay, maximal delay, buffer point, saddle-node bifurcation, complex singularity, slow--fast dynamical systems.

# aibot: parasitic masquerade; societal scale human-machine interaction.

<< This (AA) work extends recent developments in studying human--machine interaction by scaling from individual game-theoretic models to a societal-level model. (They) adopt a Graphon Mean-Field Game (GMFG) that models the interaction among four groups of internally-homogeneous but externally-heterogeneous agents in a shared environment. >>

<< (AA) results show that parasitism can masquerade as productive learning, with knowledge distribution and actions appearing healthy while being driven by machine coupling rather than independent investigation. To detect this, (They) measure the direction of information flow and belief entropy of the environment, revealing that human to machine channel dominates across all scenarios, with the asymmetry intensifying under parasitism. >>

<< (They) further demonstrate that the system exhibits coexisting mutualistic and parasitic equilibria, where environmental noise can induce a tipping point that shifts agents past the cognitive cost barrier. These emergent phenomena are not designed into any individual agent but arise from the collective interaction structure, underscoring the need to study the sociology of humans and machines holistically as a complex system. >>

Jiejun Hu-Bolz, James Stovold. Parasitic Masquerade: Societal Scale Human-Machine Interaction. arXiv: 2606.17925v1 [cs.GT]. Jun 16, 2026.

https://arxiv.org/abs/2606.17925

Also: ai, bot, artificial intelligence, analogy, noise, in https://www.inkgmr.net/kwrds.html

Keywords: ai, aibot, artificial intelligence, human--machine interaction, Graphon Mean-Field Game (GMFG), parasitism, masking, masquerade as productive learning, mutualistic and parasitic equilibria, environmental noise, sociology of humans and machines.

# gst: collective drift and pinning in active rotator networks with Kuramoto coupling and mixed-sign feedback disorder.

<< ️Active rotator models provide a minimal phase description of excitable and oscillatory systems, and have long been used to study mutual entrainment, synchronization, and collective transitions. >>

<< ️Here, (AA) investigate fully connected active rotator networks with Kuramoto coupling, where a common intrinsic drive competes with local feedback amplitudes drawn from a zero-mean Gaussian distribution. This produces a competition between local pinning and collective phase alignment. >>

<< ️Using mean absolute late-time drift and the fractions of positive and negative drifting oscillators, (They) construct numerical regime maps in the feedback-disorder-coupling plane. At weak coupling, increasing the feedback disorder strength suppresses drift, while stronger coupling can restore positive late-time drift when feedback disorder is not too strong. (They) interpret these regimes using analytical limits for the uncoupled and coherent strong-coupling cases. >>

<< ️(They) also examine finite-size effects and zero-mean distributed intrinsic frequencies. Together, these results show that mixed-sign local feedback alone can reshape the balance between pinning and drifting in coupled active rotator networks, even when the intrinsic drive is homogeneous. >>

Arpan Dey. Collective drift and pinning in active rotator networks with Kuramoto coupling and mixed-sign feedback 

disorder. arXiv: 2606.10032v1 [nlin.AO]. Jun 8, 2026.

https://arxiv.org/abs/2606.10032

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

Keywords: gst, networks, disorder, transitions, active rotator networks, excitable- oscillatory- systems, Kuramoto coupling, local feedbacks, feedback disorder.

# gst: randomised mixed labyrinth fractals.

<< ️In this (AA) paper, the class of randomised mixed labyrinth fractals is introduced. It is a class of finitely ramified Sierpinski carpets that generalize mixed labyrinth fractals. >>

<< ️The structures are generated by randomly selected labyrinth patterns with fixed selection probabilities at each iteration level, offering a flexible framework to study fractal topology, arc dimensions, and shortest path properties. Here, the focus lies on analysing how the randomised mixing of patterns - specifically their shape, symmetry, and path geometry - effects arc dimensions, path lengths, and isotropy restoration. >> 

<< ️The (AA) study reveals that isotropy, previously shown for self-similar fractals, extends to the randomised mixed class. Various scaling behaviours of shortest path dimensions with respect to the mixing probability are identified, including linear and nonlinear monotonic trends, as well as transitions with maxima. The approximated path matrix is proposed as an efficient alternative to extensive iterative simulations, reliably reproducing statistical results. >>

<< ️The findings highlight the relevance of pattern properties in determining fractal structures and dynamics and suggest applications in physical systems such as diffusion, signal processing, and antenna design. >>

Janett Prehl, Ligia Loretta Cirstea, Daniel Dick. Randomised mixed labyrinth 

fractals. arXiv: 2606.07241v1 [cond-mat.dis-nn]. Jun 5, 2026.

https://arxiv.org/abs/2606.07241

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

Keywords: gst, randomness, transitions, fractals, fractal topology, labyrinth fractals, Sierpinski carpets, randomly labyrinth patterns.

# game: apropos of “tit-for-tat” approach, the evolution of lying in a spatially-explicit prisoner's dilemma model.

<< ️(AA) present the results from a spatial model of the prisoner’s dilemma, played on a toroidal lattice. Each individual has a default strategy of either cooperating (C) or defecting (D). Two strategies were tested, including “tit-for-tat” (TFT), in which individuals play their opponent’s last play, or simply playing their default play. Each individual also has a probability of telling the truth (0 ≤ P_(truth) ≤ 1) about their last play. >>

<< ️This parameter, which can evolve over time, allows individuals to be, for instance, a defector but present as a cooperator regarding their last play. >>

<< ️This leads to interesting dynamics where mixed populations of defectors and cooperators with P_(truth) ≥ 0.75 move toward populations of truth-telling cooperators. >>

<< ️Likewise, mixed populations with P_(truth) < 0.7 become populations of lying defectors. >>

<< ️Both such populations are stable because they each have higher average scores than populations with intermediate values of P_(truth). Applications of this model are discussed with regards to both humans and animals. >> 

Gregg Hartvigsen. The Evolution of Lying in a Spatially-Explicit Prisoner's Dilemma Model. arXiv: 2602.02587v1 [physics.soc-ph]. Jan 31, 2026.

https://arxiv.org/abs/2602.02587

Also: tit-for-tat, game, in https://www.inkgmr.net/kwrds.html 

Keywords: game, tit-for-tat, prisoner's dilemma, toroidal lattice, cooperating- defecting- strategies, truth-telling cooperators, lying defectors.

# behav: decomposition of anomalous diffusion in two-state random walks.

<< ️Two-state stochastic models, where motion alternates between distinct dynamical modes, are widely observed in complex systems. Here (AA) study the Two-State Random Walk (TSRW), which switches between a continuous-time random walk (CTRW) rest state and a standard Lévy walk (LW) motion state, each with power-law distributed sojourn times. >>

<< ️Using anomalous diffusion decomposition, (They) show that TSRWs exhibit a generic coexistence of Joseph (correlation), Noah (heavy-tailed increments), and Moses (aging) effects. >>

<< ️Strikingly, although classical Lévy walks alone possess only the Joseph effect, both Noah and Moses effects emerge in TSRWs solely due to stochastic switching with the CTRW phase. >>

<< ️(Their) results demonstrate that coupling between dynamical states can fundamentally reshape the mechanisms driving anomalous diffusion, offering a minimal yet powerful framework for transport in heterogeneous and intermittently switching environments. >>

Abhijit Bera, Kevin. E. Bassler. Decomposition of Anomalous Diffusion in two-state random walks. arXiv: 2606.00149v2 [nlin.AO]. Jun 7, 2026.

https://arxiv.org/abs/2606.00149

Also: behav, random, walk, walking, in https://www.inkgmr.net/kwrds.html 

Keywords: behavior, randomness, walk, walking, two-state stochastic behavior, two-state random walk, stochastic switching, Lévy walk motion, Joseph Noah Moses effects, anomalous diffusion, heterogeneous and intermittently switching environments. 

# gst: localization of active particles on random arrays of parallel filaments.

<< ️Quenched disorder in the environment can fundamentally alter transport dynamics in both active and passive systems. (AA) explore how disordered arrays of filaments govern the distribution of intermittently moving particles which switch between diffusive and processive transport. >>

<<️ Motivated by the mixed-polarity arrangements of parallel microtubules observed in mammalian dendrites, (They) show that such arrays tend to result in localization of particles at regions of convergent filament orientation. In the rapid attachment-detachment limit, the disordered system can be described by a noisy one-dimensional effective energy landscape, whose structure is approximated by a random walk. >>

<< ️The depth and width of wells on this landscape are expressed as a function of the transport kinetics and system geometry. Localization is shown to be strongest at intermediate run-lengths, where biased transport persists long enough to sense the quenched filament polarity but not so long as to facilitate escape from local traps. >>

<< ️These (AA) results demonstrate robust localization of particles moving on random filament networks, highlighting the emergent spatial organization that arises from an interplay of active transport and quenched disorder. >>

Owen Santoso, Elena Koslover. Localization of Active Particles on Random Arrays of Parallel Filaments. arXiv: 2606.00286v1 [cond-mat.dis-nn]. May 29, 2026.

https://arxiv.org/abs/2606.00286

Also: noise, disorder, disorder & fluctuations, random, intermittency, escape, particle, in https://www.inkgmr.net/kwrds.html 

Keywords: gst, noise, disorder, disorder & fluctuations, randomness, intermittency, escape, particles, quenched disorder, transport dynamics, diffusive and processive transport, arrays of filaments, random walk, random filament networks, escape from local traps.

# gst: hierarchical crack patterns; identification of crack generations.

<< ️Hierarchical crack patterns of various origins are ubiquitous in the world around us. (AA) reduce the problem of classifying crack generations in an image of a part of the entire hierarchical crack pattern to the well-known topological sorting of a directed acyclic graph. The classification demonstrates robustness to reasonable shifts in the pattern image boundaries. >>

Yuri Yu. Tarasevich, Andrei S. Burmistrov, Andrei V. Eserkepov. Hierarchical crack patterns: Identification of crack generations. arXiv: 2606.03473v1 [cond-mat.dis-nn]. Jun 2, 2026.

https://arxiv.org/abs/2606.03473

Also: crack, fracture, in https://www.inkgmr.net/kwrds.html 

Keywords: gst, crack, fracture, fragment of hierarchical crack pattern, topological sorting, root cracks, network 

fragment, hierarchical network structure.

# gst: percolation criticality of amorphous-amorphous transitions (in compressed glasses).

<< ️The low-to-high-density transition in compressed silica glass is investigated using percolation theory. Large-scale molecular dynamics simulations of SiO glasses, (..) were carried out (by AA) to investigate the emergence of structural motifs and their growth to system-spanning length scales under compression. >>

<< ️Taken together, these results underline the consistency between the bonded and non-bonded approaches. Native tetrahedral clusters, (..) collapse according to a process close to the random percolation model. >>

<< ️For all other percolation transitions, i.e. involving clusters with higher coordination number and connectivity, the deviation of the exponents instead suggests a different universality class. It can be argued that for these structures, the transition occurs in a medium where the percolating cluster is surrounded by an infinite cluster of lower coordination and connectivity, alongside emerging clusters with higher coordination and connectivity, resulting in topological, and hence elastic, heterogeneities. This behavior recalls topological constraint theory, also known as percolation rigidity, that arises from a flexible to a rigid network as local connectivity changes >>.

Julien Perradin, Simona Ispas, Ricardo V. Paredes, et al. Percolation Criticality of Amorphous-Amorphous Transitions in Compressed Glasses. arXiv: 2606.04748v1 [cond-mat.dis-nn]. Jun 3, 2026.

https://arxiv.org/abs/2606.04748

Also: random, fluctuations, collapse, transition,  in https://www.inkgmr.net/kwrds.html 

Keywords: gst, randomness, fluctuations, collapse, transitions, percolation theory, random percolation, rigidity percolation, critical percolation, bonded and non-bonded approaches, topological constraint theory, amorphous structures, crystalline polymorphs, origin of plasticity.

# gst: effective synchronization amid noise-induced chaos.

<< ️Two remote agents with synchronized clocks may use them to act in concert and communicate. This necessitates some means of creating and maintaining synchrony. One method, not requiring any direct interaction between the agents, is to expose them to a common, environmental, stochastic forcing. This “noise-induced synchronization” occurs only under sufficiently mild forcing; stronger forcing disrupts synchronization. >>

<< ️(AA) investigate the regime of strong noise, where the clocks' relative phases evolve chaotically. Using a simple realization of disruptive noise, (They) demonstrate effective synchronization. First, although the relative phases of the two clocks varied erratically, (They) confirm that they became statistically independent of initial conditions and hence equivalent after a well-defined timescale. Second, (They) show that an agent can estimate an effective phase that closely agrees with the other's phase. Thus, synchronization is practically attainable beyond the regime of conventional noise-induced synchronization. >>

Benjamin Sorkin, Thomas A. Witten. Effective synchronization amid noise-induced chaos. Phys. Rev. E 113, 054215. May 19, 2026.

https://journals.aps.org/pre/abstract/10.1103/rqgs-99d9

arXiv: 2505.08942v3 [cond-mat.stat-mech]. Feb 22, 2026.

https://arxiv.org/abs/2505.08942

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

Keywords: gst, noise, chaos, transitions, noise-induced transitions, noise-induced synchronization, noise-induced chaos, synchronization transition, kick, kicked trajectory.

# gst: superflows around corners.

<< ️(AA) investigate analytically and numerically the dynamics of a two-dimensional superflow governed by the Gross-Pitaevskii equation passing over finite-size rectangular obstacles: an impenetrable wall and an impenetrable rectangular well. >>

<< ️Extending classical studies of vortex nucleation around smooth obstacles, (They) focus on the role of sharp corners in determining the onset of vortex nucleation. Using a combination of analytical techniques based on the Schwarz-Christoffel methods for potential flow and on numerical simulations, (They) show that local velocity amplification near sharp corners crucially controls the critical flow velocity for vortex nucleation. For both wall and well configurations, (They) identify analytically and theoretically the critical velocities as a function of the obstacle width and its height or depth, finding excellent agreement between the theory and numerical simulations. >>

<< ️(Their) results provide a simple  framework for understanding superflow stability past finite-size obstacles with sharp features, and they are directly relevant to experimentally realizable configurations in atomic Bose-Einstein condensates and related superfluid systems. >>

Thomas Frisch, Christophe Josserand, Sergio Rica. Superflows around corners. Phys. Rev. Fluids 11, 054703. May 20, 2026.

https://journals.aps.org/prfluids/abstract/10.1103/77hn-2hqf

arXiv:2602.18876v1 [cond-mat.quant-gas]. Feb 21, 2026.

https://arxiv.org/abs/2602.18876

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

Keywords: gst, vortex, vortex nucleation, two-dimensional superflow. 

# gst: describing a universal critical behavior in a transition from order to chaos.

<< ️(AA) present a comprehensive discussion of a transition from integrability to nonintegrability in an oval billiard with a static boundary. This transition is controlled by a deformation parameter 𝜀, which modifies the boundary shape from circular, corresponding to 𝜀=0 and an integrable dynamics, to oval for 𝜀≠0, where nonintegrability emerges. >>

<< ️The deformation of the circular billiard gives rise to a chaotic layer that develops along a well-defined stripe in phase space. By introducing a set of transformations that isolate this chaotic stripe, (They) characterize the diffusive spreading of ensembles of trajectories and identify an observable, 𝜔_(rms,sat), which plays the role of an order parameter for the transition. >>

<< For small deformations, the saturation value of the diffusion obeys the scaling law 𝜔_(rms,sat)∝𝜀^(˜𝛼), with a critical exponent ˜𝛼=0.507⁢(2), vanishing continuously as 𝜀→0. The associated susceptibility, 𝜒=𝑑⁢𝜔_(rms,sat)/𝑑⁢𝜀, diverges in the same limit, signaling the presence of critical behavior analogous to that observed in second-order (continuous) phase transitions in statistical mechanics. >>

Edson D. Leonel, Mayla A. M. de Almeida, Juan Pedro Tarigo, et al. Describing a universal critical behavior in a transition from order to chaos. Phys. Rev. E 113, 054220. May 28, 2026.

https://journals.aps.org/pre/abstract/10.1103/7231-j7zv

arXiv: 2602.17810v1 [nlin.CD]. Feb 19, 2026.

https://arxiv.org/abs/2602.17810

Also: billiard, transition, order, disorder, chaos, in https://www.inkgmr.net/kwrds.html 

Keywords: gst, billiard, oval billiard, transitions, order, disorder, elementary excitations, small deformations, topological defects, criticality, chaotic stripes, chaos.

# gst: orbital instability and spanwise vortex structure of unstable periodic orbits in large-eddy simulations of plane Couette flow.

<< ️(AA) perform an unstable periodic orbit (UPO) analysis of moderately developed Couette turbulence with large-eddy simulations (LES) using a static eddy viscosity model. >>

<< ️(They) find that spanwise vortices, stretched between streamwise rolls, approach the walls, over which new spanwise vortices are generated. The stretching of these vortices is driven by strong shear layers induced by the streamwise rolls. This vortex-generation mechanism, as revealed by the LES UPOs, is a significant dynamical process in LES turbulence at high Reynolds numbers. >>

<< ️By computing local Lyapunov exponents, which quantify the least stable perturbation growth rates along the UPOs, (They) show that the stretching process amplifies their growth. The corresponding Lyapunov vectors highlight the instability of prominent shear layers through which the stretched spanwise vortices emerge between the rolls. >>

<< ️(Their) results suggest that high-strain-rate structures in developed turbulence play a central role in shaping the geometrical structure of turbulent orbits in phase space. >>

Eiichi Sasaki, Javier Jiménez, Genta Kawahara. Orbital instability and spanwise vortex structure of unstable periodic orbits in large-eddy simulations of plane Couette flow. Phys. Rev. Fluids 11, 054603. May 14, 2026.

https://journals.aps.org/prfluids/abstract/10.1103/mtw2-29r3

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

Keywords: gst, instability, turbulence, vortex, spanwise vortices, eddy viscosity model, unstable periodic orbit (UPO), streamwise rolls, stretching process.

# gst: apropos of interfacial contact events, bounce or coalescence, a physical learning frame.

<< ️In this study, (AA) develop an interface-contact simulation framework based on physical criteria and machine-learning-assisted classification to describe coalescence and bouncing within a unified formulation. The framework realizes interfacial coalescence and bouncing through the fusion and generation of multiple volume-of-fluid fields. When adjacent interfaces are predicted to coalesce, multiple VOF fields are collapsed into a single VOF field. When approaching interfaces are predicted to bounce, a single VOF field is regenerated into multiple VOF fields, allowing the interfaces to continue evolving independently. >>

<< With this treatment, the difficulties associated with topological transition, regime-map identification, increasing computational demand, and stochastic behavior during interfacial approach are separated from the interface-tracking procedure. These decisions are instead assigned to a physics-guided machine-learning model with strong adaptability. This strategy avoids the direct resolution of an ultrathin gas film and reduces the dependence on empirical molecular-force parameters. >>

<< ️Simulations of droplet--droplet collisions show that the proposed framework can reproduce both coalescence and bouncing over different impact conditions. By further introducing a drainage-time criterion, the framework is extended to the simulation of droplet impact on a liquid surface. For this problem, the numerical results agree well with both previous experimental observations and the present experiments. >>

<< ️Moreover, the framework captures the complete sequence of bouncing followed by subsequent coalescence within a single simulation, These (AA) results demonstrate that the proposed framework has strong adaptability for interfacial contact problems and provides a unified modeling route for droplet coalescence, bouncing. >>

J.H. Xu, Z.L. Wang. Bounce or coalescence: a physical learning frame. arXiv: 2605.15844v1 [physics.flu-dyn]. May 15, 2026. 

https://arxiv.org/abs/2605.15844

Also: drop, droplet, droploid, in https://www.inkgmr.net/kwrds.html 

Keywords: gst, drops, droplets, droploids, coalescence, bouncing, volume-of-fluid (VOF) field, transitions, topological transitions, stochasticity, droplet--droplet collisions, interfacial contact events, 

# gst: multi-cluster chimeras in phase oscillators with repulsive nonlocal coupling.

<< ️Local repulsive coupling tend to a desynchronize ensembles of globally coupled oscillators, but when the repulsive coupling is nonlocal, multi-cluster chimeras can result. In this case, several groups of synchronized oscillators (the so-called clusters) are formed, and these coexist with a set of desynchronized oscillators. >>

<< ️For phase oscillators on a ring with nonlocal piecewise linear repulsive coupling that also involves a phase lag, (AA) find that in the multi-cluster chimera state the synchronized clusters are either antiphase or in splay with respect to each other, namely the n consecutive synchronized clusters differ in phase by 2π/n. >>

<< ️This is in contrast to multi-cluster chimeras that are formed with nonlocal attractive coupling. The synchronized solutions are studied numerically as well as analytically and by analysing their stability, (They) identify the parameter regions where these can be observed. (Their) numerical results are validated by dimensional reduction using the Ott-Antonsen analysis. >>

Ayushi Saxena, Sangeeta Rani Ujjwal, Ram Ramaswamy. Multi-cluster chimeras in phase oscillators with repulsive nonlocal coupling. arXiv: 2605.15628v1 [nlin.AO]. May 15, 2026.

https://arxiv.org/abs/2605.15628

Also: chimera, stability, in https://www.inkgmr.net/kwrds.html 

Keywords: gst, chimera, stability, coupled oscillators, repulsive coupling, multi-cluster chimeras. 

# gst: formation of mechanical rogue waves.

<< ️Rogue waves, characterized by their abrupt and extreme localization in space and time, have evolved from maritime folklore to subjects of intense study across diverse fields, from hydrodynamics and nonlinear optics to plasmas and condensed matter physics. In mechanical systems, however, experimental realization remains elusive despite theoretical and numerical predictions. This gap stems from the stringent requirements for controllable nonlinearity, the high-fidelity initialization of the system, and the necessity to overcome inherent energy dissipation. >>

<< ️Here, (AA) report the experimental formation of mechanical rogue waves in a precisely engineered one-dimensional metamaterial lattice with tailored nonlinearity and minimal dissipative losses. Using a precision electromagnetic release system, (They) prescribe initial strain profiles that trigger a transition from dispersive decay to extreme wave focusing. >>

<< ️(Their) parametric analysis reveals that the emergence of these extreme events is strictly contingent upon a synergy between high nonlinearity and a broad spatial energy reservoir within the initial seed. Crucially, neither factor alone is sufficient to overcome dispersion and trigger the observed focusing. >> 

<< ️These findings establish a robust platform for studying transient nonlinear wave focusing phenomena in mechanical systems and offer insights for harnessing extreme wave localization for applications such as energy harvesting, waveguiding, and mechanical signal processing. >>

Yasuhiro Miyazawa, Christopher Chong, Panayotis G. Kevrekidis, et al. Formation of mechanical rogue waves. arXiv: 2605.18518v1 [nlin.PS]. May 18, 2026.

https://arxiv.org/abs/2605.18518

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

Keywords: gst, waves, rogue waves, mechanical rogue waves, transitions.

# gst: spin-hair induced chaos of spinning test particles in rotating hairy black holes.

<< ️(AA) investigate the finite-time instability of massive spinning test particles around a rotating hairy black hole generated through gravitational decoupling. (They) show that spin–curvature coupling and the hairy geometry can shift the evolved orbit away from the requested seed parameters, making the empirical orbital map essential for interpreting the dynamics. >>

<< Small-spin and geodesic trajectories remain close to regular behavior, whereas large-spin trajectories show stronger finite-time growth. A scan of the (S,β) plane shows that the instability does not grow monotonically, but appears in localized regions where the particle spin and the radial profile of the hair act cooperatively. Thus, the hairy background does not simply rescale the Kerr result; it reorganizes the strong-field phase-space region sampled by spinning particles. >>

Surojit Dalui, Xian-Hui Ge. Spin-Hair Induced Chaos of Spinning Test Particles in Rotating Hairy Black Holes. arXiv: 2605.19673v1 [gr-qc]. May 19, 2026.

https://arxiv.org/abs/2605.19673

Also: black hole, instability, particle, chaos, in https://www.inkgmr.net/kwrds.html 

Keywords: gst, black hole, instability, particle, chaos, rotating hairy black hole.

# gst: free-surface deformations induced by three-dimensional turbulence.

<< ️(AA) report the experimental characterization of free-surface deformations generated by three-dimensional homogeneous and isotropic turbulence. Using Fourier transform profilometry in a jet-forced turbulent tank, (They) perform spatiotemporal measurements of the surface elevation field over a wide range of turbulence intensities. >>

<< ️The standard deviation of surface deformations scales linearly with subsurface velocity fluctuations. The spectra of surface deformations highlight the coexistence of two mechanisms: transient coherent structures (e.g., upwelling) contributing to the low-frequency, large-scale spectral components, and a passive response to subsurface turbulent pressure fluctuations responsible for the power-law spectral scaling. The wavenumber and frequency spectra of surface deformations exhibit similar power-law exponents (−2.5), suggesting the advection of turbulent structures at the free surface. >> 

<< ️(They) develop a linear response model based on the transfer function from the free surface to turbulent pressure fluctuations, incorporating wave-turbulent damping. The model successfully predicts the main features of the turbulent surface: spatiotemporal spectrum shape, similar spectrum power-law exponents (−7/3), and dominance of passive response over wave generation. These findings provide new insights into free-surface turbulence in regimes where turbulent velocities remain below the surface-breaking threshold. >>

Michaël Berhanu, Eric Falcon. Free-surface deformations induced by three-dimensional turbulence. arXiv: 2605.13654v1 [physics.flu-dyn]. May 13, 2026.

https://arxiv.org/abs/2605.13654

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

Keywords: gst, free-surface turbulence, free-surface deformations, subsurface velocity fluctuations, wave-turbulent damping, surface-breaking threshold.

# gst: apropos of control by noise, diffusive transport from spatially correlated random phase kicks.

<< ️(AA) study the dynamics of a single-particle wave packet on a one-dimensional lattice subject to periodic random phase kicks with finite spatial correlation length. This stroboscopic setting provides a controllable model of dephasing in driven quantum systems. >>

<< ️Using a momentum-space formulation, (They) show that the evolution is governed by an accumulated phase whose structure determines the spreading of the wave packet. (They) find that the phase kicks strongly suppress ballistic transport and induce diffusion at long times. (They) derive an explicit analytical expression for the diffusion coefficient as a function of the correlation length, in excellent agreement with numerical simulations. >>

<< (Their) results uncover a simple mechanism by which spatially correlated phase noise controls quantum transport, and provide a quantitatively testable prediction for diffusion in periodically driven lattice systems. Possible experimental realizations in cold-atom platforms are discussed. >>

Pei Wang. Diffusive transport from spatially correlated random phase kicks. arXiv: 2605.06701v1 [cond-mat.mes-hall]. May 5, 2026.

https://arxiv.org/abs/2605.06701

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

Keywords: gst, particle, waves, randomness, noise, single-particle wave packet, periodic random phase kicks, spatially correlated phase noise, quantum transport.

# music: rhythm as an ordered phase of sound; how musical meter emerges in a statistical mechanical model.

<< ️(AA) develop a model of musical rhythm and meter based on optimizing the trade-off between human psychological preferences for perceiving repeated patterns in time with a desire for variety and complexity. >>

<< ️By mapping these competing preferences onto analogous quantities in statistical physics, (They) define an effective free energy which is minimized in the grand canonical ensemble. Using a mean field approximation, (They) observe phase transitions in the model from disordered events in time to orderings that closely reproduce those seen in music. >>

<< ️(They) then compare the range of rhythmic characteristics predicted by the model to a data set drawn from compositions by Johann Sebastian Bach, finding generally good quantitative agreement. The results provide a lens through which to study musical rhythm and a method for generatively producing rhythms. >>

Robert St. Clair, Jesse Berezovsky. Rhythm as an ordered phase of sound: How musical meter emerges in a statistical mechanical model. Phys. Rev. E 113, 054116. May 11, 2026.

https://journals.aps.org/pre/abstract/10.1103/kjfs-v245

arXiv: 2604.07476v1 [cond-mat.stat-mech]. Apr 8,2026.

https://arxiv.org/abs/2604.07476

Also: music, sound, jazz, brain, in https://www.inkgmr.net/kwrds.html 

Keywords: music, sound, jazz, brain, musical rhythms, perceiving repeated patterns, desire for variety and complexity, phase transitions, disordered events, J.S. Bach.

# gst: from chaos to synchrony in recurrent excitatory-inhibitory networks with target-specific inhibition.

<< ️Biological neural networks can operate in qualitatively distinct dynamical regimes, and transitions between these regimes are thought to underlie changes in computation and behavior. The seminal work of Sompolinsky, Crisanti, and Sommers (SCS) showed that random recurrent networks undergo a transition from quiescence to asynchronous chaos, establishing a paradigmatic link between random connectivity, dynamical instability, and internally generated fluctuations in neural circuits. >>

<< ️Here, (AA) extend this framework to two-population firing-rate networks with segregated excitatory and inhibitory neurons and target-specific inhibitory couplings that break excitation--inhibition balance. Using dynamical mean-field theory, (They) derive self-consistent equations for the macroscopic mean activities and autocorrelations, together with stability criteria distinguishing mean-driven and fluctuation-driven instabilities. (They) show that target-specific inhibition organizes the phase diagram into three qualitative classes: inhibition-dominated or strictly balanced networks display only quiescent activity and asynchronous chaos; excitation-dominated networks display persistent activity together with either synchronous chaos with non-vanishing mean activity or coherent oscillations, depending on the stability-matrix eigenvalues. >>

<< Crucially, coherent oscillations do not coexist with chaotic fluctuations around the periodic mean trajectory; rather, their onset suppresses the chaotic component, reminiscent of input-induced suppression of chaos. These results generalize SCS theory to recurrent networks with explicit excitatory--inhibitory structure and identify target-specific inhibition as a key control parameter for large-scale neural dynamics. >>

Carles Martorell, Rubén Calvo, Alessia Annibale, et al. From Chaos to Synchrony in Recurrent Excitatory-Inhibitory Networks with Target-Specific Inhibition. arXiv: 2605.14916v1 [cond-mat.dis-nn]. May 14, 2026.

https://arxiv.org/abs/2605.14916

Also: network, fluctuations, instability, transition, chaos, in https://www.inkgmr.net/kwrds.html 

Keywords: gst, networks, fluctuations, instability, transitions, chaos, biological neural networks, random recurrent networks, asynchronous chaos, excitation--inhibition balance, target-specific inhibition.

# gst: rigorous ultimate scaling in rapidly rotating steady convection.

<< ️Rapidly rotating Rayleigh-Bénard convection admits a class of exact steady single-mode solutions describing high-amplitude convection cells. Using a matched asymptotic analysis in the high-Rayleigh-number limit, (AA) obtain a rigorous characterization of their bulk and boundary-layer structure, yielding explicit scaling laws for the Nusselt and Reynolds numbers, including their dependence on the horizontal wavenumber. >>

<< (They) show that, for suitable wavenumbers, these solutions attain the diffusivity-free ultimate scalings frequently assumed for geophysical and astrophysical convection, with additional enhancing logarithmic corrections. This reveals a specific mechanism through which rapidly rotating convection can approach ultimate heat transport via coherent columnar structures with well-defined horizontal scales. >>

Gabriel Hadjerci, Shingo Motoki, Genta Kawahara. Rigorous ultimate scaling in rapidly rotating steady convection. arXiv: 2605.05574v1 [physics.flu-dyn]. May 7, 2026.

https://arxiv.org/abs/2605.05574

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

Keywords: gst, waves, vortex, convection, convection cells, Rayleigh-Bénard convection, bulk and boundary-layer structure, rotation, rotating convection.

# gst: delay-induced chimera transitions via mode selection in a multiplex FitzHugh Nagumo network.

<< ️(AA) investigate delay-induced collective dynamics in a two-layer multiplex FitzHugh Nagumo network with nonlocal intra layer coupling and delayed inter layer interactions. While delay effects are often treated as secondary, (They) show that deterministic inter-layer delay alone can act as a control mechanism for spatial coherence. >>

<< ️Through systematic numerical simulations, (They) observe a clear transition as the delay parameter increases: fragmented incoherence evolves into chimera-like partial coherence, and eventually into a coherent traveling-wave state. This transition is consistently captured by spatial snapshots, space-time plots, and mean phase velocity profiles. >>

<< ️To explain this behavior, (They) analyze the stability of spatial Fourier modes and show that the delay term introduces a mode-dependent exponential factor in the characteristic equation. This term induces non-monotonic changes in modal stability, effectively acting as a mode-selection mechanism: intermediate delays selectively destabilize a subset of modes, producing chimera-like coexistence, while larger delays suppress incoherent modes and restore global coherence. >>

<< ️(Their) results demonstrate that inter-layer delay provides a simple and robust mechanism for controlling pattern formation in multiplex excitable networks, offering new insight into delay driven synchronization phenomena. >>

Hui Wu. Delay-induced chimera transitions via mode selection in a multiplex FitzHugh Nagumo network. arXiv: 2605.04430v1 [physics.bio-ph]. May 6, 2026.

https://arxiv.org/abs/2605.04430

Also: chimera, network, transition, waves, pause, in https://www.inkgmr.net/kwrds.html 

Keywords: gst, chimera, networks, transitions, waves, pause, delay, inter-layer delay, delay-induced collective dynamics, two-layer multiplex excitable network.

# gst: apropos of dissipation of fast tides, turbulent damping of fast tidal oscillations by three-dimensional Rayleigh-Bénard convection with a radiating free surface.

<< ️(AA) present three-dimensional Dedalus simulations of Rayleigh–Benard convection with a blackbody-radiating free upper surface, subject to a low-amplitude oscillatory forcing that mimics tidal perturbations in convective envelopes of stars and planets. The forcing period is 10–100 times shorter than the convective timescale, tconv. Using a Reynolds decomposition of the velocity field averaged over one oscillation period, in which the tidal oscillations naturally constitute the fluctuating field and xconvection the mean flow, (They) elucidate the kinetic energy exchange between the two. >>

<< ️Provided the oscillatory Reynolds number exceeds a modest threshold, (They) find that the oscillations systematically transfer kinetic energy to the mean flow at a volume-averaged rate D_R∼u′^(2)t^−1_conv, where u′ is the rms fluctuation velocity. This reflects strong, order-unity correlations between the fluctuation velocities and the mean flow. These arise because the oscillatory forcing displaces fluid elements that are then redirected by buoyancy and incompressibility in the same manner as the mean flow. >>

<< The transfer is dominated by correlations involving vertical velocity fluctuations and vertical gradients of the mean flow. The resulting energy transfer rate is consistent, within the equilibrium-tide framework, with the observed tidal circularisation of solar-type binaries and with the orbital evolution of moons of Jupiter and Saturn. This validates the formalism proposed by Terquem (2021) for the dissipation of fast tides, a longstanding problem. Replacing the free surface with a rigid upper boundary significantly and artificially modifies the correlations. >>

Caroline Terquem, Alexander Boone, Enrico Martinez. Turbulent damping of fast tidal oscillations by three-dimensional Rayleigh-Bénard convection with a radiating free surface. arXiv: 2605.05108v1 [astro-ph.SR]. May 6, 2026.

https://arxiv.org/abs/2605.05108

Also: turbulence, fluctuations, dissipation,  in https://www.inkgmr.net/kwrds.html 

Keywords: gst, turbulence, fluctuations, dissipation, turbulent damping, tidal oscillations, tidal perturbations, Rayleigh-Bénard convection, dissipation of fast tides.

# gst: apropos of packing regimes, understanding the dynamics of evaporation-driven colloidal self-assembly.

<< ️Complex colloidal cluster morphologies are desirable for the fabrication of advanced materials, such as photonic crystals and meta-materials, and can be formed through evaporation-driven packing. By coupling lattice Boltzmann and discrete element methods, here (AA) elucidate the rich interplay between fluid and particle dynamics during evaporation-driven self-assembly of spherical colloidal particles. >>

<< ️(They) construct a regime diagram for a wide range of evaporation rates, interparticle friction coefficients, and particle numbers, identifying parameter regimes for open, closed, and minimal moment of inertia cluster configurations. >>

<< ️Analyzing the competition between capillary, hydrodynamic, normal, and friction forces, (They) show that interparticle friction can exert a disproportionately strong influence on the final packing outcome despite being considerably smaller in magnitude than other forces at play. (Their) simulation results further highlight the potential for tuning colloidal cluster configurations via their dynamic trajectories. >>

Junyu Yang, Abhinav Naga, Xitong Zhang, et al. Understanding the Dynamics of Evaporation-Driven Colloidal Self-Assembly. arXiv: 2605.04878v1 [cond-mat.soft]. May 6, 2026.

https://arxiv.org/abs/2605.04878

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

Keywords: gst, particle, self-assembly, evaporation, spherical colloidal particles, complex colloidal clusters, evaporation-driven packing, evaporation-driven self-assembly, interparticle friction coefficients, minimal moment of inertia, tuning colloidal cluster configurations.

# gst: critical parameters of an oval billiard with an elliptical component.

<< ️(AA) explore the critical parameters responsible for the transition from integrability to chaos in a family of billiards combining elliptical and oval deformations. Unlike standard oval billiards, where a known critical parameter governs the destruction of the last invariant curve, the introduction of an integrable elliptic component yields a second deformation axis. >>

<< (They) derive an analytical expression for the critical parameter in this combined system and validate it numerically using Slater's theorem, showing that increasing the elliptical component lowers the critical threshold for global chaos. >>

<< ️Moreover, (They) uncover a previously unexplored regime: when the two deformation components are in phase, the elliptic contribution progressively suppresses chaos, leading to the restoration of invariant curves and periodic orbits. A first-order analytical approximation confirms this behavior, supported by numerical validation. >>

<< ️(Their) results reveal how the interplay between distinct boundary deformations enriches phase-space organization and offers enhanced controllability of chaotic dynamics in billiard systems. >>

Anne Kétri P. da Fonseca, Joelson D. V. Hermes, Edson D. Leonel. Critical parameters of an oval billiard with an elliptical component. arXiv: 2605.00145v1 [nlin.CD]. Apr 30, 2026. 

https://arxiv.org/abs/2605.00145

Also: billiard, transition, chaos, in https://www.inkgmr.net/kwrds.html 

Keywords: gst, billiard, transition, chaos, criticality, elliptical and oval deformations. 

# gst: topological defects in spiral wave chimera states.

<< ️Chimera states, characterized by the coexistence of coherent and incoherent domains, represent a paradigm of self-organization in complex systems. In this study, (AA) introduce a topological analysis method based on winding numbers to characterize the dynamics of spiral wave chimeras in a two-dimensional phase oscillator network. >>

<< ️(Their) investigation reveals distinct scaling laws governing the system's evolution across the phase lag 𝛼. Perturbation analysis in the limit 𝛼→0 demonstrates that the incoherent core radius scales linearly with 𝛼. In contrast, within the stable chimera regime, the average total positive winding number 𝜇 follows a clear exponential growth law 𝜇=𝑎⁢𝑒^(𝑏⁢𝛼). This scaling disparity signals a physical crossover from a regime dominated by geometric core expansion to one driven by active topological excitation. >> 

<< ️Furthermore, (They) identify a statistical transition in the defect distribution from binomial-like to Poisson-like behavior at a critical threshold 𝛼*. These results demonstrate that topological defects possess intrinsic statistical order, establishing 𝜇 as a robust macrovariable for analyzing the structural complexity of chimera states. >>

Lintao Liu, Nariya Uchida. Topological defects in spiral wave chimera states. Phys. Rev. E 113, 054207. May 8, 2026.

https://journals.aps.org/pre/abstract/10.1103/yhbq-ztk8

arXiv: 2511.21058v2 [nlin.AO]. 5 Mar 2026.

https://arxiv.org/abs/2511.21058

Also: chimera, waves, self-assembly, transition, network, defect, in https://www.inkgmr.net/kwrds.html 

Keywords: gst, chimera, waves, self-assembly, transition, network, defect, topology, spiral wave chimeras, two-dimensional phase oscillator network, active topological excitations, topological defects. 

# gst: apropos of smallest amplitude perturbations that trigger transition to turbulence, the minimal seeds in the Stokes boundary layer.

<< ️Minimal seeds, the smallest amplitude perturbations that trigger transition to turbulence, are presented in the Stokes boundary layer, the oscillating flow of a viscous fluid above a flat plate. The minimal seed trajectories are dominated by the Stokes boundary layer's large linear transient growth at early times, but only 73% of the initial energy is formed from the linearly optimal growing mode; the remainder ensures that nonlinear interaction transfers energy from spanwise- to streamwise- independent structures, and makes up for a timing mismatch between the end of linear transient growth and the production phase of the edge state (the saddle point separating laminar and turbulent basins of attraction). >>

Tom Eaves. Minimal seeds in the Stokes boundary layer. arXiv: 2604.23213v1 [physics.flu-dyn]. Apr 25, 2026.

https://arxiv.org/abs/2604.23213

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

Keywords: gst, turbulence, transitions, minimal seeds, laminar and turbulent basins of attraction.

# gst: capillary slinky; equilibrium and dynamics of a droplet in a soft spring.

<< ️Springs can be found in many applications and biological systems, and when these are soft, they easily deform. At small scales, capillarity can induce a force leading to spring deformations when the elastocapillary number is small. >>

<< ️ (AA) demonstrate through experiments the nontrivial equilibrium-shape liquid droplets adopt in these soft springs, which form an annulus, eruciform, and spherical shapes. When these droplets are set in motion, they display different flow regimes with significant dissipation generated by the internal rotational flow. >>

<< ️The static and dynamics of droplets in such a capillary slinky are also used to demonstrate how surface tension can actuate springs by stretching/compression, while providing a way for active flow control in soft springs. >>

Bidisha Bhatt, Andreas Carlson. Capillary slinky: Equilibrium and dynamics of a droplet in a soft spring. Phys. Rev. Fluids 11, 043607. Apr 29, 2026.

https://journals.aps.org/prfluids/abstract/10.1103/p9j4-hp5h

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

Keywords: gst, drops, droplets, droploids, capillarity, capillary slinky, spring deformations, annulus, eruciform, spherical shapes, rotational flows.

# gst: apropos of unsteady two-dimensional flows, the Lagrangian rotating contracting structures.

<< ️(AA) identify materially defined regions in unsteady two-dimensional flows that combine finite-time contraction with elevated accumulated intrinsic rotation along trajectories, which (They) term Lagrangian rotating contracting structures (LRCS). These regions are detected using existing objective diagnostics—the Lagrangian-averaged vorticity deviation (LAVD) together with direct tests of material contraction—without relying on the geometry of LAVD level sets. >>

<< ️In strongly deforming flows, LAVD maxima need not correspond to vortical regions or be enclosed by regular level sets, rendering geometry-based identification unreliable. Nevertheless, regions exhibiting inward spiraling motion and contraction can be extracted by combining LAVD with a contraction criterion. >>

<< ️Applications to atmospheric and oceanic flows show that such behavior arises both in twisted LAVD fields generated at submesoscales and in mesoscale flows where it is enhanced by inertial effects, with finite-time contraction providing the dynamical constraint that isolates materially organized regions with elevated intrinsic rotation. >>

F.J. Beron-Vera. Lagrangian Rotating Contracting Structures. arXiv: 2604.25036v1 [nlin.CD]. Apr 27, 2026.

https://arxiv.org/abs/2604.25036

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

Keywords: gst, vortex, instability, finite-time contraction, accumulated intrinsic rotation, Lagrangian rotating contracting 

structures, inward spiraling motion.

# gst: chaotic billiard lasers.

<< ️This chapter provides an overview of chaotic billiard lasers as a prominent branch of quantum chaos. These lasers offer an ideal experimental platform for demonstrating the principles of quantum chaos within a physical system. >>

<< ️(AA) begin by introducing the fundamental principles of chaotic ray dynamics in optical microcavities, where the transition from regular to fully chaotic dynamics fundamentally alters the underlying wavefunctions and lasing properties. A central focus is placed on "chaos-assisted light emission," which serves as a practical manifestation of "chaos-assisted tunneling" -- a hallmark phenomenon in the study of quantum chaos. >>

<< ️(They) discuss both theoretical frameworks and experimental validations, demonstrating how chaotic orbits facilitate the coupling between evanescently localized modes and far-field emission. >>

<<️ Furthermore, exploring how the presence of a gain medium influences established results from quantum chaos research remains a fundamental and intriguing problem in physics. To address this, (They) establish a rigorous and comprehensive derivation of the Maxwell-Bloch equations for two-dimensional microcavity lasers, specifically examining their application to fully chaotic, stadium-shaped billiard lasers. >>

<< ️By bridging the gap between nonlinear lasing processes and chaotic wavefunctions, this chapter highlights the unique potential of chaotic billiards for controlling light-matter interactions and shaping the next generation of unconventional coherent light sources. >>

Takahisa Harayama. Chaotic Billiard Lasers. arXiv: 2604.23614v1 [quant-ph]. 26 Apr 26, 2026.

https://arxiv.org/abs/2604.23614

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

Keywords: gst, billiard, billiard laser, waves, transitions, chaos, quantum chaos, chaotic billiard, chaos-assisted light emission, chaos-assisted tunneling. 

# gst: self-mediation of runaway electrons via self-excited wave-wave and wave-particle interactions.

<< ️Nonlinear dynamics of runaway electron induced wave instabilities can significantly modify the runaway distribution critical to tokamak operations. Here (AA) present a fully kinetic simulation of runaway-driven instabilities toward nonlinear saturation in a warm plasma where collisional damping is subdominant. >>

<< ️It is found that the slow-X modes grow an order of magnitude faster than the whistler modes, and they parametrically decay to produce whistlers much faster than those directly driven by runaways. These parent-daughter waves, as well as secondary and tertiary wave instabilities, initiate a chain of wave-particle resonances that strongly diffuse runaways to the backward direction. This reduces almost half of the current carried by high-energy runaways, over a time scale orders of magnitude faster than experimental shot duration. These results beyond quasilinear analysis may impact anisotropic energetic electrons broadly in laboratory, space, and astrophysics. >>

Qile Zhang, Yanzeng Zhang, Qi Tang, et al. Self-mediation of runaway electrons via self-excited wave-wave and wave-particle interactions. Phys. Rev. E 113, L043203. Apr 20, 2026.

https://journals.aps.org/pre/abstract/10.1103/k3bq-cvjs

arXiv: 2409.15830v2 [physics.plasm-ph]. Mar 7, 2026.

https://arxiv.org/abs/2409.15830

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

Keywords: gst, waves, whistler waves, instability, particles, collisional damping, wave-particle resonance

# brain: hippocampus can rewires itself even after a single experience.

<< ️Understanding how brains learn and remember remains among the most important challenges in science. Recent studies in the hippocampus implicate a new form of synaptic plasticity, named behavioral timescale synaptic plasticity (BTSP), in the generation of experience-based learning and memory. BTSP is a strong, bidirectional type of plasticity that affects synaptic weights over many seconds of time. It is induced by single dendritic plateau potentials, as opposed to many action potentials, and is thus capable of producing new place cells in one trial. Plateau potential initiation is controlled, at least in part, by local feedback inhibition and an instructive input from a higher-order brain region that potentially links the plasticity to current experience.  >>

<< ️The new credit assignment procedure in BTSP provides a nonstandard mechanism for memory storage and retrieval that could mitigate the need for widespread synapse stabilization. In addition, it may allow hippocampal networks both to form memories of specific behavioral episodes and to generalize on the basis of past episodes. Finally, recent BTSP investigations could provide a basis for future explorations into how brains learn and remember, ranging from the systems and cognitive levels down to the basic biochemical building blocks of learning and memory. >>

Jeffrey C. Magee. Behavioral timescale synaptic plasticity: properties, elements and functions. Nature Neurosci 29; 520–534. Feb 20, 2026.

https://www.nature.com/articles/s41593-026-02214-2

Antoine D. Madar, Aaron D. Milstein, Thomas J. O’Dell, et al. Behavioral Timescale Synaptic Plasticity: A Burst in the Field of Learning and Memory. J. Neurosci .45 (46) e1332252025. Nov 12,  2025.

https://www.jneurosci.org/content/45/46/e1332252025

Yasemin Saplakoglu. A New Type of Neuroplasticity Rewires the Brain After a Single Experience. quantamagazine.org. Apr 24, 2026.

https://www.quantamagazine.org/a-new-type-of-neuroplasticity-rewires-the-brain-after-a-single-experience-20260424/

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

Keywords: brain, dance,  hippocampus, synaptic plasticity, behavioral timescale synaptic plasticity (BTSP), learning, memory, single dendritic plateau potentials, local feedback inhibition.

# gst: twin satellites and ring bubbles from coalescing magnetically levitated air bubbles in water.

<< ️(AA) investigate the ejection of satellite bubbles during the coalescence of two air bubbles in water. Using magnetic levitation (They) suspend the bubbles, with diameters in the range 3–15 mm, in a stable, neutrally buoyant state, free from mechanical constraints. >>

<< ️(Their) experiments reveal the simultaneous ejection of twin satellite bubbles from the poles of the bubble formed from the coalescence of equal-sized precursors. More generally, (They) find that the number and size of the ejected satellites are dependent on the initial size ratio of the precursor bubble pair. Numerical simulations, which agree well with (Their) experiments, show that satellite production is governed by the combined effect of two distinct processes: the arrival of a capillary wave crest at a pole and the rapid retraction of that polar region. >>

<< ️(They) propose a timing model that successfully predicts the range of size ratios for which single, double, or no satellites are formed. (Their) analysis also offers insight into the absence of satellite ejection in similarly sized liquid drop coalescence. Furthermore, (They) report the experimental observation of toroidal bubble ejection from precursor bubbles with approximately 2:1 diameter ratios, and (They) show that the formation of these toroidal bubbles is also governed by (Their) timing model. >>

N. Sampara, G. Hunter-Brown, K. A. Baldwin, et al. Twin satellites and ring bubbles from coalescing magnetically levitated air bubbles in water. Phys. Rev. Fluids 11, 043605. Apr 22, 2026.

https://journals.aps.org/prfluids/abstract/10.1103/fr1q-m1j9

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

Keywords: gst, waves, capillary wave crest, drops, bubbles, twin satellite bubbles, toroidal bubbles, drop coalescence, satellite ejection.

# gst: transient chaos and Rayleigh particle escape out of a time modulated optical trap.

<< ️(AA) consider Rayleigh particles in a periodically modulated optical trap formed by two counterpropagating Gaussian beams. It is shown that for certain values of the parameters the system exhibits transient chaos which manifests itself in particle acceleration and subsequent directional ejection out of the trap. The escape flights are terminated at a distance of hundreds of wavelengths from the trap center and the particles return to the trap under the action of the Stokes force. The particle escape is shown to be a threshold effect that can be potentially employed for particle sorting. >>

Evgeny N. Bulgakov, Konstantin N. Pichugin, Dmitrii N. Maksimov. Transient chaos and Rayleigh particle escape out of a time modulated optical trap. Phys. Rev. E 113, 044216. Apr 23, 2026.

https://journals.aps.org/pre/abstract/10.1103/fj7q-vm5b

arXiv:2512.03403v1 [nlin.CD]. Dec 3, 2025.

https://arxiv.org/abs/2512.03403

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

Keywords: gst, chaos, transitions, particle, escape, periodically modulated trap, threshold effect.

# gst: chaotic ghosts in systems with parameter drift; delay and control critical transitions.

<< ️In dynamical systems with a time-dependent parameter, i.e., parameter drift, after crossing a saddle-node bifurcation, the so-called ghost state formed by the disappeared equilibria or periodic orbit can influence transient dynamics, causing a delayed transition. >>

<< ️This phenomenon has been investigated previously. However, the effect of chaotic ghosts on the critical transition in drifting systems has been less studied. In this paper, (AA) explore how chaotic ghosts and drifting rates influence critical transitions from the perspective of the ensemble. >> 

<< ️The (AA) results reveal the mechanism of the delayed transition related to chaos and how trajectories on the initial ensemble composed of a chaotic attractor transition to a qualitatively different object during the drift. In addition, (They) quantify the delayed transition and further find that the delay follows a power-law scaling with respect to the drifting rate. Finally, (AA) show that the critical transition is fully avoided as long as the reversal rate of the parameter exceeds a certain critical rate, even though the bifurcation point has been crossed. >>

Han Su, Denghui Li, Jicheng Duan, et al. Chaotic ghosts in systems with parameter drift: Delay and control critical transitions. Phys. Rev. E 113, 044207. April 13, 2026.

https://journals.aps.org/pre/abstract/10.1103/bdf8-wkpm

Also: chaos, attractor, transition,  in https://www.inkgmr.net/kwrds.html 

Keywords: gst, chaos, attractor, transitions, chaotic attractor transition, chaotic ghosts, criticality, critical transitions, bifurcation point, saddle-node bifurcation, ghost state, transient dynamics, delay, delayed transition, drifting rate.

# gst: quantum kicked top; a paradigmatic model

<< ️The quantum kicked top (QKT) is one of the most widely studied models in quantum chaos, providing a minimal yet powerful framework for exploring the relationship between classical nonlinear dynamics and quantum behavior. Unlike many chaotic systems with infinite-dimensional Hilbert spaces, the QKT possesses a finite-dimensional Hilbert space, making it analytically and numerically controllable while still showing a rich dynamical phenomena. >>

<< ️(AA) present a comprehensive introduction to the QKT as a paradigmatic model of quantum chaos. Starting from the classical kicked top, (They) derive the discrete nonlinear map governing the dynamics on the unit sphere and analyze its phase space structure through fixed points, stability analysis, bifurcations and Lyapunov exponents. (They) then discuss the role of symmetries, including rotational and time-reversal symmetry, and how their breaking modifies the dynamics. >>

<< ️By linking classical phase space structures with quantum dynamical indicators, the QKT provides a clear setting to investigate the emergence of chaotic behavior in the semiclassical limit. The chapter, therefore, highlights the quantum kicked top as a bridge between nonlinear classical dynamics, quantum chaos and modern quantum information science. >>

Avadhut V. Purohit, Udaysinh T. Bhosale. Quantum Kicked Top: A Paradigmatic Model. arXiv: 2604.12345v1 [quant-ph]. Apr 14, 2026.

https://arxiv.org/abs/2604.12345

Also: chaos, entropy, in https://www.inkgmr.net/kwrds.html 

Keywords: gst, chaos, entropy, quantum kicked top, quantum chaos, bifurcations, rotational symmetry, time-reversal symmetry, entanglement, qubits, quantum information, entanglement entropy.