# gst: impact of spinning droplets onto superhydrophobic surfaces: asymmetric tumbling rapid rebound.

<< ️The impact dynamics of spinning droplets onto superhydrophobic surfaces was studied by using Volume-of-Fluid simulations, covering broad ranges of Weber number (We) and dimensionless angular velocity (Ω). >>

<< ️Results show that, the spinning motion of droplets leads to two novel rebound scenarios. Specifically, the front-raise tumbling rebound occurs at a lower (Ω) and is caused by the unsymmetrical Laplace pressure, while the rear-raise tumbling rebound emerges at a higher (Ω) and is attributed to the rotational inertia. The angular momentum of the spinning droplet is dissipated or even reversed, while its direction upon detachment is inconsistent with the visually observed spinning motion. >>

<< ️With the increase of the angular velocity, the droplet-wall contact time is largely reduced, which is attributed to the asymmetric spreading by the spinning motion rather than the increased kinetic energy. A theoretical model was also established to predict asymmetric spreading and the contact time and validated against numerical results in wide ranges of (We) and (Ω).  >>

Jinyang Wang, Feifei Jia, et al. Impact of Spinning Droplets onto Superhydrophobic Surfaces: Asymmetric Tumbling Rapid Rebound. arXiv: 2507.13150v1 [physics.flu-dyn]. Jul 17, 2025. 

https://arxiv.org/abs/2507.13150

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

Keywords: gst, drops, droplets, droploids

# gst: topologically nontrivial multicritical points.

<< ️Recently, the intriguing interplay between topology and quantum criticality has been unveiled in one-dimensional topological chains with extended nearest-neighbor couplings. In these systems, topologically distinct critical phases emerge with localized edge modes despite the vanishing bulk gap. >>

<< ️In this work, (AA) study the topological multicritical points at which distinct gapped and critical phases intersect. Specifically, (They) consider a topological chain with coupling up to the third nearest neighbors, which shows stable localized edge modes at the multicritical points. These points possess only nontrivial gapped and critical phases around them and are also characterized by the quadratic dispersion around the gap-closing points. >>

<< Further, (AA) analyze the nature of zeros in the vicinity of the multicritical points by calculating the discriminants of the associated polynomial. The discriminant uniquely identifies the topological multicritical points and distinguishes them from the trivial ones.  >>

AA << finally study the robustness of the zero-energy modes at the multicritical points at weak disorder strengths, and reveal the presence of a topologically nontrivial gapless Anderson-localized phase at strong disorder strengths. >>

Ranjith R Kumar, Pasquale Marra. Topologically nontrivial multicritical points. arXiv: 2507.11120v1 [cond-mat.dis-nn]. Jul 15, 2025.

https://arxiv.org/abs/2507.11120

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

Keywords: gst, disorder, disorder & fluctuations, criticality, multicritical points, transition.

# gst: apropos of drift surfaces, e.g., banana orbits, perturbed toroidal vortices display internal simply connected topology.

<< ️This (AA) work shows that the interiors of perturbed zero-helicity vortices display simply connected topology with a crescent-shaped boundary. Flux surfaces in fluid and magnetic vortices were explored analytically, while particle trajectories in the context of plasma confinement were examined numerically, demonstrating the existence of both toroidal and simply connected topologies. >>

<< ️Numerical simulations of particle trajectories were conducted in the context of fusion confinement to calculate particle trajectories in a perturbed Soloviev equilibrium where simply connected flux surfaces were observed. The orbits often displayed crescent shapes, yet showed several marked differences from the flux surfaces, e.g., gyro-radii of size comparable to the crescent diameter, asymmetric crescents, connections between well-separated crescent tips, and possibly toroidal shapes, with an inversion of the roles played by the major and minor axes. >>

<< ️This new topology appears for perturbations in a broad class, with amplitudes and spatial variance allowed to be arbitrarily small. A corollary of this work proves the closedness of field lines under odd-parity perturbations of zero-helicity vortices. >>

Taosif Ahsan, Samuel A. Cohen, Alan H. Glasser. Perturbed Toroidal Vortices Display Internal Simply Connected Topology. arXiv: 2507.04596v1 [math-ph]. Jul 7, 2025. 

https://arxiv.org/abs/2507.04596

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

Keywords: gst, vortex, particle, transition, foliated torus, toroidal vortices, banana orbits. 

# gst: the turbulence development at its initial stage, a scenario based on the idea of vortices decay.

<< ️In this paper, a model of the development of a quantum turbulence in its initial stage is proposed. The origin of the turbulence in the suggested model is the decay of vortex loops with an internal structure. >>

AA << ️consider the initial stage of this process, before an equilibrium state is established. As result of (Their) study, the density matrix of developing turbulent flow is calculated. The quantization scheme of the classical vortex rings system is based on the approach proposed by the author earlier. >>

S.V. Talalov. The turbulence development at its initial stage: a scenario based on the idea of vortices decay. arXiv: 2303.05908v3 [physics.flu-dyn]. Feb 16, 2024.

https://arxiv.org/abs/2303.05908

Also: << Lo "smoothing" e', nell' essenziale, un atteggiamento, un comportamento piu' o meno automatico, una tecnica, una prassi. (..) tutte le volte che uno "smoother" livella un vortice (piu' verosimilmente crede di aver circoscritto un vortice per livellarlo), se non e' accorto (non lo e' quasi mai) mentre cerca di spianare lo potenzia e, allo stesso tempo - questo e' il fatto curioso - puo' avere inconsapevolmente generato i presupposti per accenderne in prospettiva almeno un' altro. Oppure altri due. Oppure 'n'. >> In: Smoothers. Notes (quasi-stochastic poetry). Mar 27, 2006.

http://inkpi.blogspot.com/2006/03/1980-smoothers.html

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

Keywords: gst, turbulence, vortex.

# gst: irreversibility in scalar active turbulence, the role of topological defects.

<< ️In many active systems, swimmers collectively stir the surrounding fluid to stabilize some self-sustained vortices. The resulting nonequilibrium state is often referred to as active turbulence, by analogy with the turbulence of passive fluids under external stirring. Although active turbulence clearly operates far from equilibrium, it can be challenging to pinpoint which emergent features primarily control the deviation from an equilibrium reversible dynamics. >>

Here, AA << reveal that dynamical irreversibility essentially stems from singularities in the active stress. Specifically, considering the coupled dynamics of the swimmer density and the stream function, (AA) demonstrate that the symmetries of vortical flows around defects determine the overall irreversibility. (Their) detailed analysis leads to identifying specific configurations of defect pairs as the dominant contribution to irreversibility. >>

Byjesh N. Radhakrishnan, Francesco Serafin, et al. Irreversibility in scalar active turbulence: The role of topological defects. arXiv:2507.06073v1 [cond-mat.stat-mech]. Jul 8, 2025.

https://arxiv.org/abs/2507.06073

Also: swim, turbulence, vortex, self-assembly, chaos, clinamen, in https://www.inkgmr.net/kwrds.html 

Keywords: gst, swim, swimmers, turbulence, active turbulence, vortex, self-assembly, chaos, defects, topological defects, deviation, clinamen.

# gst: noise reinstates collapsed populations; stochastic reversal of deterministic extinction.

<< ️Conventional wisdom suggests that environmental noise drives populations toward extinction. In contrast, (AA) report a paradoxical phenomenon in which stochasticity reverses a deterministic tipping point, thereby preventing collapse. Using a hybrid model that integrates logistic growth with a density-triggered sigmoidal collapse, (They) uncover a striking reversal: deterministic fragility on one side, and stochastic rescue under weak noise on the other. >>

AA << analysis demonstrates that noise disrupts the convergence of deterministic trajectories toward extinction by altering the phase space topology, enabling back-transitions to viable states. This mechanism gives rise to noise-induced metastability and reveals a form of stochastic robustness not captured by deterministic models. >>

<< ️These findings suggest that natural fluctuations can serve as a stabilizing force in complex systems, offering a compelling counter-narrative to classical models in ecology, epidemiology, and beyond. (AA) advocate for a re-evaluation of stabilization strategies, emphasizing the constructive role of stochasticity in averting population collapse. >>

Vinesh Vijayan, B Priyadharshini, et al. Noise reinstates collapsed populations: stochastic reversal of deterministic extinction. arXiv:2507.03954v1 [q-bio.PE]. Jul 5, 2025.

https://arxiv.org/abs/2507.03954

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

Keywords: gst, noise, weakness, disorder,  

fluctuations, tipping point, transitions, stochasticity, stochastic reversal, stochastic rescue. 

# gst: self-feedback delay induces extreme events in the theoretical Brusselator system.

AA << ️present a study of the theoretical Brusselator model with time-delayed self-feedback, demonstrating its ability to induce extreme events when delays in reaction processes significantly influence subsequent dynamics, with and without diffusion. >>

<< ️Stability analyses reveal the mechanisms driving this behavior with respect to the delay time. The occurrence of extreme events is validated using various numerical and statistical tools, including phase portraits, time series, probability distribution functions, return periods, and spatiotemporal evolution. >>

<< ️A comprehensive two-parameter scan delineates the parameter regimes where the extreme events emerge, alongside the identification of transient chaos within specific regions of the parameter space. To confirm these numerical findings, (AA) constructed an analog electronic circuit that emulates the model, providing experimental validation of the predicted dynamics. >>

S. V. Manivelan, S. Sabarathinam, et al. Self-feedback delay induces extreme events in the theoretical Brusselator system. Phys. Rev. E 112, 014202. Jul 1, 2025.

https://journals.aps.org/pre/abstract/10.1103/v1h2-42w1

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

Keywords: gst, Brusselator system, self-feedback, delay, chaos, transient chaos, transitions, extreme events.