# gst: topological phase transition driven by structural defects.

<< ️Structural defects, such as disclinations and dislocations, destroy the long-range crystalline order as they proliferate. In this work, (AA) continuously drive a system from a crystalline state on a decorated honeycomb lattice to a hyperuniform amorphous state, by consecutively introducing Stone-Wales (SW) defects, which can be viewed as dipoles of dislocations. >>

<< ️Using a topological Weaire-Thorpe Hamiltonian model to describe electrons in this system, (AA) demonstrate that SW defects can cause pseudo-band inversions and, correspondingly, a reversal of the Chern number. Using adiabatic arguments and a computationally efficient spillage indicator, (They) predict the topological phase diagram of the amorphous state from the crystalline one. (They) explain the nature of the pseudo-band inversion through the renormalization of the hopping in an effective Hamiltonian based on a single SW defect. >>

Andrii Syrota, Andrej Mesaros, Pascal Simon. Topological phase transition driven by structural defects. arXiv: 2609.26586v1 [cond-mat.dis-nn]. Sep 22, 2026. 

https://arxiv.org/abs/2609.26586

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

Keywords: gst, defect, order, disorder, transitions, structural defects, 

disclinations, dislocations, dipoles of dislocations, amorphous states, pseudo-band inversions.

# gst: disorder-promoted stability.

<< Previous studies of network dynamics have suggested that heterogeneity among nodes inhibits stability, at odds with the ubiquity of inherently heterogeneous natural and engineered systems. >>

<< ️Here, (AA) show that this conclusion arises from model reductions introduced for mathematical tractability and breaks down when nodal dynamics are higher-dimensional, yielding non-Hermitian Jacobians. In such systems, including neural, power-grid, and material networks, nodal heterogeneity can instead enhance stability, even when parameters are randomly disordered. >>

<< ️Non-Hermiticity also underlies the stabilizing effects of network heterogeneity, which can arise even in one-dimensional nodal dynamics through nonreciprocal interactions, as shown for ecological networks. >>

<< ️(AA) framework reveals disorder not as a liability but as a general resource for stabilizing complex systems. >>

Arthur N.Montanari, Pietro Zanin, Adilson E.Motter. Disorder-promoted stability. arXiv: 2609.25226v1 [cond-mat.dis-nn]. Sep 21, 2026.

https://arxiv.org/abs/2609.25226

Science. 393: 6817, 1241-1249. Sep 17, 2026. DOI: 10.1126/science.aeg3946.

https://www.science.org/doi/10.1126/science.aeg3946

Also: noise, disorder, network, game, poetry, in https://www.inkgmr.net/kwrds.html 

Keywords: gst, noise, disorder, networks.

# gst: mixing, anisotropy, and Lagrangian dispersion in Rayleigh-Taylor turbulence under variable acceleration.

<< ️This (AA) study investigates miscible Rayleigh-Taylor (RT) turbulence subjected to gravity removal or reversal at different stages of its development, using high-resolution numerical simulations and Lagrangian passive-particle tracking. The state of the mixing layer at the switching time, particularly its thickness and turbulent intensity, is shown to control the subsequent evolution. >>

<< ️Gravity reversal transforms the unstable RT layer into a weakly turbulent, stably stratified flow with a thick mixed region. The vertical mass flux and kinetic-energy anisotropy exhibit decaying oscillations whose characteristic period increases with the mixing-layer thickness at reversal and is described by the Brunt-Väisälä frequency. >>

<< ️In contrast, gravity removal eliminates further buoyancy production without imposing a restoring force, allowing the mixing layer to continue broadening through inertial coasting while retaining the large-scale structure inherited from the preceding RT stage. The Lagrangian analysis distinguishes absolute material transport from relative turbulent stirring. >>

<< ️After gravity removal, the vertical velocity correlation remains positive over a comparatively long interval, sustaining both single-particle displacement and particle-pair separation. Gravity reversal instead drives the correlation through zero and induces particle oscillations consistent with the Brunt-Väisälä timescale, thereby suppressing both absolute transport and the relative stretching of initially neighboring particles. >>

<< ️These (AA) results show that the postswitch dynamics are governed jointly by the flow state at the switching time and by whether the modified forcing preserves or actively destroys vertical velocity memory. >>

Dongxiao Zhao, Gaojin Li. Mixing, anisotropy, and Lagrangian dispersion in Rayleigh-Taylor turbulence under variable acceleration. Phys. Rev. Fluids 11, 093903. Sep 18, 2026.

https://journals.aps.org/prfluids/abstract/10.1103/r4vw-jkyc

Also: Dongxiao Zhao, Gaojin Li. Evolution of Rayleigh-Taylor turbulence under vorticity and strain-rate control. arXiv: 2506.07012v1 [physics.flu-dyn]. Jun 8, 2025.

https://arxiv.org/abs/2506.07012

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

Keywords: gst, particles, turbulence, Lagrangian dispersion, Rayleigh-Taylor turbulence, anisotropy, reversal, buoyancy, inertial coasting, particle-pair separation, particle oscillations, vertical velocity memory, Rayleigh-Taylor instability, turbulent mixing.

# gst: rupture dynamics of dense granular films; from liquidlike bursting to solidlike fracturing.

<< ️(AA) investigate the bursting dynamics of dense granular films punctured at imposed controlled liquid pressure. Using high-speed imaging, (They) reveal a two-stage opening process.️ At early times, the hole expands in a liquidlike manner with a nearly circular shape and a constant velocity, though significantly lower than the Taylor-Culick speed. This velocity is modeled by a balance between surface tension and effective surface viscosity, which depends on particle size and liquid depression. >>

<< ️(AA) show that as liquid pressure decreases, the initial opening slows down progressively until it ultimately reaches a jamming state. As the opening progresses, the film undergoes a transition to a solidlike regime, where faceting occurs due to fracture propagation within the granular skeleton. >>

<< ️(AA) show that the characteristic fracture size follows a 𝑡3/4 scaling, consistent with a balance between surface energy release and viscous dissipation induced by liquid redistribution within the 2D granular network. ️These findings advance (Their) understanding of the mechanics of granular films and their transition between fluidlike and solidlike behaviors. >>

Paul Gauthier, Nabil Retailleau, Yacine Khidas, et al. Rupture dynamics of dense granular films: From liquidlike bursting to solidlike fracturing. Phys. Rev. Fluids 11, 094301. Sep 8, 2026.

https://journals.aps.org/prfluids/abstract/10.1103/c9bz-d2yg

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

Keywords: gst, particles, fracture, crack, drops, droplets, droploids, bubbles, transitions, fluid-particle interactions, granular fluids, granular films, granular network, bursting dynamics, surface tension, surface viscosity, viscous dissipations, jamming states, surface energy.

# gst: odd slip at chiral active surfaces.

<< ️Odd slip at solid-liquid interfaces, characterized by a velocity component perpendicular to the applied shear stress, introduces a novel class of odd transport phenomena with transverse momentum transfer at boundaries, distinct from odd viscosity, odd elasticity, or odd diffusivity. This effect arises on chiral active surfaces with persistent energy input and defined handedness, such as carpets of rotating biological or synthetic cilia with flexible anchoring. Although odd slip itself is dissipationless, its maintenance comes at an energetic cost, which we estimate from the microscopic model. With respect to its orientation dependence, odd slip can be classified as pseudo-scalar or pseudo-vectorial. >>

<< ️(AA) use a perturbative expansion to determine the resistance tensors of problems with different levels of broken symmetries. They reveal how the surface chirality and body asymmetry together violate the Onsager symmetry, but uphold the Onsager-Casimir reciprocity. Strikingly, suspensions of particles with odd slip embedded in a conventional Newtonian bulk fluid exhibit odd viscosity, providing a new minimal mechanism for its emergence beyond current microscopic models. >>

Yuto Hosaka, Andrej Vilfan. Odd slip at chiral active surfaces. arXiv: 2609.17005v2 [cond-mat.soft]. Sep 16, 2026. 

https://arxiv.org/abs/2609.17005

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

Keywords: gst, particles, solid-liquid interfaces, chiral active surfaces, surface chirality, parity-violating phenomena, shear stress, odd viscosity, odd diffusivity, odd elasticity, odd slip, broken symmetries. 

# gst: how turbulent flows grow vorticity at a point.

<< ️(AA) describe how strong vorticity fluctuations appear in three-dimensional incompressible turbulence driven by a large-scale random force. By combining analytical and numerical methods, (They) construct a vorticity instanton: the most probable force history driving the flow to a prescribed large vorticity at a given point and time. >>

<< ️(AA) show how the smooth, large-scale force produces a long vortex filament with a thin, viscous-scale core. (Their) main finding is that the standard mechanism of amplifying a vortex tube through radial compression and axial stretching is only effective up to a threshold value. Producing vorticity above the threshold requires an additional ingredient: vorticity waves propagating along the tube. >>

<< ️The final vorticity is the result of two colliding waves. This mechanism has striking similarities to the one recently suggested by OpenAI for creating infinite vorticity in finite-time Navier--Stokes blow-up. >>

Timo Schorlepp, Vladimir Rosenhaus, Gregory Falkovich. How turbulent flows grow vorticity at a point. arXiv: 2609.13056v1 [physics.flu-dyn]. Sep 11, 2026.

https://arxiv.org/abs/2609.13056

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

Keywords: gst, vortex, turbulence, randomness, waves, vorticity instanton, vortex filaments, colliding waves.

# gst: extreme events in an active fluid medium.

<< ️(AA) observe the emergence of extreme events in an active fluid involving two distinct chemical species that regulate active stress. One species is slow diffusing and the other is fast diffusing, and the growth of the fast-diffusing species is modelled using a nonlinear logistic term. >>

<< ️(AA) demonstrate the presence of extreme events in the temporal evolution of the concentrations, as well as in the spatial profile of the system,in regimes of merging-emerging soliton-like dynamics and spatio-temporal chaos, through analysis of the time-series, bifurcation diagrams, probability distribution functions of the concentration of the two species, return maps and distributions of inter-event intervals. >>

<< ️Interestingly, (They) also find evidence of pronounced bunching of extreme events and super-extreme events in the slow chemical species in the soliton-like regime. (They) go on to systematically explore the dependence of the extreme event occurrences on the Péclet number and the strength of the nonlinear growth term, and find that the probability of extreme events increases after a critical Péclet number, while increasing the nonlinearity suppresses extreme events. >>

<< ️Lastly, in order to gain further insight, (AA) investigate a modified mode-truncated reduced order model comprising of coupled differential equations mimicking this active fluid system. (They) find that this reduced order model also exhibits extreme events whose emergence is correlated with a sudden expansion in attractor size due to a crisis arising from attractor collision. >>

<< ️So these results demonstrate the existence of extreme events in an active fluid system, and are of potential relevance to biological phenomena where active transport plays an important role. >>

Joydeep Das, Abhishek Chaudhuri, Sudeshna Sinha. Extreme Events in an Active Fluid Medium. arXiv: 2609.14334v1 [nlin.PS]. Sep 13, 2026.

https://arxiv.org/abs/2609.14334

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

Keywords: gst, chaos, solitons, attractors, extreme events, merging-emerging soliton-like dynamics, soliton-like regimes, criticality, active transport.