# life: apropos of birth-and-death processes, framework for fluctuating times and counting observables in stochastic excursions.

<< ️Many natural systems exhibit dynamics characterized by alternating phases or recurring sets of states. Describing the fluctuations of such systems over stochastic trajectories is necessary across diverse fields, from biological motors to quantum thermal machines. >>

<< ️In an accompanying Letter, (AA) introduced the notion of stochastic excursions−a framework to analyze out of equilibrium processes via sub-trajectories. Through counting observables, this framework captures finite-time fluctuations and trajectory-level behavior, which provides insights into thermodynamical trade-offs between thermodynamic quantities of interest, such as entropy production and dynamical activity. >>

<< ️In this work, (AA) enhance this formalism by providing a suite of technical results on how to efficiently compute excursion-related quantities. (Their) analytical results provide explicit formulas for general moments of counting variables and excursion duration, as well as their covariance and conditional moments. (They) show that excursion statistics recover full counting statistics results, and uncover a relation between fluctuations of counting observables at single-excursion level and the steady state diffusion coefficient (noise). >> 

<< ️(AA) also discuss a fluctuation theorem for individual excursions and show that it implies a modified thermodynamic uncertainty relation at the excursion level. In addition, (They) explore how analyzing excursions and using the results developed here can yield insights into three problems of interest: the three-qubit absorption refrigerator, cellular sensing, and birth-and-death processes. >>

Guilherme Fiusa, Pedro E. Harunari, Abhaya S. Hegde, et al. Framework for fluctuating times and counting observables in stochastic excursions.

Phys. Rev. E 114, 024129. Aug 13, 2026.

https://journals.aps.org/pre/abstract/10.1103/jydr-1853

arXiv: 2506.05160v3 [cond-mat.stat-mech]. Aug 19, 2026.

https://arxiv.org/abs/2506.05160

Also: Guilherme Fiusa, Pedro E. Harunari, Abhaya S. Hegde, et al. Counting observables in stochastic excursions. Phys. Rev. E 114, L022102 (2026). 

https://journals.aps.org/pre/abstract/10.1103/1blp-2b27

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

Keywords: walk, walking, noise, uncertainty, behavior, fluctuations, randomness, stochasticity, stochastic excursions, Nomads. 

# gst: emergence of minimal chimera in uncoupled oscillators under common frequency-modulated driving.

<< (AA) report the experimental realization of minimal chimera states in a system of three uncoupled oscillators driven solely by frequency-modulated forcing. Unlike conventional scenarios where chimera states emerge due to interactions among oscillators, here the coexistence of coherent and incoherent dynamics arises entirely from a common external modulation of a system parameter. By tuning the modulation amplitude and frequency, the system exhibits transitions between global synchronization, global incoherence, and minimal chimera states. >>

<< The stability of these regimes is quantified using the maximal Lyapunov exponent, while a synchronization order parameter is employed to characterize the degree of coherence. A systematic exploration of the parameter space reveals well-defined regions associated with distinct dynamical behaviors. To provide analytical understanding, (AA) employ a phase-reduction approach and derive the corresponding phase dynamics, which elucidate the mechanisms underlying phase locking and desynchronization. The robustness of the proposed mechanism is further demonstrated in a time-delayed chaotic system. >>

<< Finally, experimental results obtained from an electronic circuit realization confirm the emergence of minimal chimera states under frequency-modulated driving. These findings establish external modulation as a viable route to chimera formation without coupling, offering a new perspective on collective dynamics in driven nonlinear systems. >>

Debabrata Biswas, Tanmoy Banerjee. Emergence of minimal chimera in uncoupled oscillators under common frequency-modulated driving: theory and experiment. arXiv: 2607.25449v1 [nlin.CD]. Jul 28, 2026.

https://arxiv.org/abs/2607.25449

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

Keywords: gst, chimera, transition, chaos, three uncoupled oscillators, coherent- incoherent dynamics, frequency-modulated forcing, global synchronization, global incoherence, minimal chimera states.

# gst: stability of vortex lattices in rotating flows.

<< Vortex lattices—highly ordered arrays of vortices—are known to arise in quantum systems such as type II superconductors and Bose-Einstein condensates. More recently, similar arrangements have been reported in classical rotating fluids. However, the mechanisms governing their formation, stability, and eventual breakdown remain poorly understood. >>

<< (AA) explore the dynamical stability of vortex lattices in three-dimensional rotating flows. To that end (They) construct controlled initial conditions consisting of vortex lattices superimposed on turbulent backgrounds. (They) then characterize their evolution across different Rossby numbers and domain geometries. >>

<< By introducing an Ekman drag (AA)  are able to reach a steady state where vortex lattices persist with near constant amplitude up until spontaneous breakup of the lattice, or an equivalent of “melting,” occurs. (They) examine an ensemble of runs in order to determine the mean lifetime of the lattice as a function of the system parameters. >>

<< (AA) results reveal that the stability of the lattices is a memory-less random process whose mean lifetime depends sensitively on the system parameters that if finely tuned can lead to very long-lived lattice states. These metastable states exhibit statistical properties reminiscent of critical systems and can offer insight into long-lived vortex patterns observed in planetary atmospheres. >>

Julián Amette Estrada, Alexandros Alexakis, Marc E. Brachet, et al. Stability of vortex lattices in rotating flows. Phys. Rev. Fluids 11, 074401. Jul 10, 2026. 

https://journals.aps.org/prfluids/abstract/10.1103/k8zw-s6kj

arXiv: 2510.06374v1 [physics.flu-dyn]. Oct 7, 2025.

https://arxiv.org/abs/2510.06374

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

Keywords: gst, vortex, turbulence, randomness, vortex lattices, rotating flows, mean lifetime, spontaneous breakups, memory-less random process, metastable states, criticality.

# gst: spatially heterogeneous noise restructures flocking into geometry-locked and vortex states.

<< ️Spatially heterogeneous environments continually challenge the ability of active matter to sustain coherent collective motion. Understanding how collective motion remains robust under changing environments is central to both the functioning of biological systems and the design of smart active matter. >>

<< ️Here, (AA) extend the Vicsek model to include a circular non-noisy region surrounded by a noisy environment - a configuration in which the noise difference sets up a contrast in local directional order between the two regions. (They) find that, as the surrounding noise is increased, the system passes through three distinct dynamical regimes: (i) conventional global flocking at low noise; (ii) geometry-locked motion, aligned with simulation boundaries, at intermediate noise; and (iii) vortical motion within the non-noisy region at high noise. >>

<< Extending the environment to multiple non-noisy regions, (AA) find that the geometry-locked regime can develop a directional coupling, while the vortex mode leads to antiferromagnetic order between the regions. Taken together, (Their) results demonstrate that the spatial modulation of order and disorder offers a powerful and generic strategy for steering active matter, aligning with recent experimental observations of active particles in patterned landscapes. >>

Ankush Semwal, Mahak Poonia, Pintu Patra. Spatially heterogeneous noise restructures flocking into geometry-locked and vortex states. arXiv: 2607.05870v1 [cond-mat.soft]. Jul 7, 2026.

https://arxiv.org/abs/2607.05870

Also: particle, noise, vortex, order, disorder, in https://www.inkgmr.net/kwrds.html 

Keywords: gst, particle, noise, vortex, order, disorder, active matter, steering active matter, coherent collective motion, noisy environment, vortical motion, geometry-locked regime. 

# life: apropos of bifurcations from stable consensus to periodic multiconsensus, consensus-breaking global Hopf bifurcation in memory-based Multi-Agent Systems.

<< ️This (AA) dissertation provides the first systematic study of symmetric consensus-breaking bifurcation to periodic multiconsensus in multi-agent systems. It analyzes this for three classes of multi-agent systems based on three different types of memory, whose closed-loop dynamics equations form delay differential equations of retarded type, neutral type, and pseudoneutral type - a subclassification of retarded type equations introduced in this dissertation which bridges retarded and neutral type delay equations. >>

<< ️Equivariant twisted degree is used to analyze the symmetric global Hopf bifurcation problem in these systems, i.e. bifurcation from a stable consensus to periodic multiconsensus. This shows how the effects of memory allow self-organizing agents to move beyond mere stationary consensus. Theoretical results for the global Hopf bifurcation and symmetric classification of periodic multiconsensus solutions across all three systems are provided, and numerical results are conducted to both validate and enhance the theoretical predictions by providing stability information on the branches which is not obtainable by the degree alone. >>

<< These principles are demonstrated in three real-world applications: one involving the control of formations of UAVs (Unmanned Aerial Vehicles), allowing them to maintain their overall spatial relationships while dancing in complex selectable oscillations; and two more in networked asset markets featuring different traders with different memory-based strategies, showing how similar mechanisms can be responsible for economic cycles of bubbles and crashes. >>

<< Finally, (AA) also numerically investigate resonant double Hopf bifurcations in the neutral delay system, showing strong evidence of a breakdown to chaos via the Ruelle-Takens-Newhouse scenario and the existence of riddled basins. >>

Casey Maikalani Crane. Consensus-Breaking Global Hopf Bifurcation in Memory-Based Multi-Agent Systems. Dissertation. The University of Texas at Dallas. Aug 2026. Supervising Professor: Wieslaw Krawcewicz, Chair.  arXiv: 2607.02388v1 [math.DS]. Jul 2, 2026.

https://arxiv.org/abs/2607.02388

Also: network, swarm, bubble, crack, chaos, transition, dance, in https://www.inkgmr.net/kwrds.html 

Keywords: life, gst, networks, swarm, bubbles, crack, chaos, transitions, dance, multi-agent systems, symmetric consensus-breaking bifurcation, stable consensus, periodic multiconsensus, symmetric global Hopf bifurcation, self-organizing agents, economic cycles of bubbles and crashes, riddled basins. 

# gst: quadruple decomposition of boundary vorticity flux.

<< ️First introduced by Lighthill in 1963 for two-dimensional flows and later generalized by Jie-Zhi Wu to three-dimensional scenarios since 1986, the boundary vorticity flux (BVF) is the cornerstone of boundary vorticity dynamics, which quantifies the vorticity source strength on a solid boundary. Recent advances in vorticity and vortex dynamics have revealed both the rigid-rotation and spin modes of vorticity from multiple perspectives. >>

<< ️In the present study, (AA) propose a novel quadruple decomposition of the BVF on a stationary solid wall, which essentially uncovers the boundary creation rates of the elementary vorticity modes for both the tangential and wall-normal BVF components, respectively. >>

<< The proposed framework is illustrated through skin-friction and surface-pressure measurements for flow over a hill model in a low-speed wind tunnel, revealing a set of intriguing BVF patterns for the first time. These theoretical results are expected to be valuable for global surface flow diagnostics when combined with experiments, as well as for understanding the formation mechanisms of near-wall coherent structures and flow-induced noise. >>

Tao Chen, Tianshu Liu. Quadruple decomposition of boundary vorticity 

flux. arXiv: 2606.28761v1 [physics.flu-dyn]. Jun 27, 2026. 

https://arxiv.org/abs/2606.28761

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

Keywords: gst, vortex, noise, transitions, boundary vorticity dynamics, boundary vorticity flux (BVF), skin-friction, 

surface-pressure, near-wall coherent structures, flow-induced noise. 

# gst: sudden expansion stability thresholds modified by lateral flows.

<< ️(AA) study the flow in a symmetric three-dimensional confined sudden expansion with lateral inflow at Reynolds number below 300 and varying lateral-to-central flow rate ratio, using experiments, linear stability analysis, weakly nonlinear theory, and direct numerical simulations. >>

<< ️Three distinct flow regimes are identified. Outside an intermediate band of lateral-to-central flow rate ratio, the flow undergoes a steady symmetry-breaking bifurcation above a critical Reynolds number, deflecting the central jet toward one side wall; weakly nonlinear analysis shows this bifurcation to be supercritical, excepting a very narrow parametric range. Within the intermediate band, no such critical Reynolds number exists and direct numerical simulations confirm that residual velocity asymmetries reflect the imposed geometric imperfections rather than intrinsic amplification. Fluctuations observed experimentally in the intermediate band of lateral-to-central flow rate ratio remain unexplained and warrant further investigation. >>

T. Salamon, R. Debuysschère, A. Chafaï, et al. Sudden expansion stability thresholds modified by lateral flows. arXiv: 2606.30269v1 [physics.flu-dyn]. Jun 29, 2026.

https://arxiv.org/abs/2606.30269

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

Keywords: gst, particles, instability, transitions, fluctuations, criticality, bifurcations, supercritical bifurcations, geometrical defects.

# gst: uncertainty growth in stably stratified turbulence.

<< ️(AA) investigate uncertainty growth and chaotic dynamics in statistically steady, stably stratified three-dimensional turbulence. Using direct numerical simulations of the Boussinesq equations, (They) quantify the divergence of initially infinitesimal perturbations via twin simulations and decorrelator diagnostics. >>

<< ️At short times, perturbations exhibit exponential growth, allowing us to define a (largest) Lyapunov exponent. (AA) systematically examine how this exponent depends on stratification strength, quantified by the Brunt-Väisälä frequency and the Froude number, in a parameter regime relevant to oceanic flows. >>

<< (They) find that increasing stratification leads to a monotonic reduction of the Lyapunov exponent, indicating suppressed chaoticity. Despite this reduction, uncertainty growth retains the universal temporal sequence observed in homogeneous isotropic turbulence—initial decay, exponential growth, and saturation. The growth phase is characterized by self-similar decorrelator spectra, but exhibits strong anisotropy: uncertainty spreads much more slowly along the stratification direction than horizontally, with the disparity increasing with stratification strength. >>

<< ️An analysis of the decorrelator evolution equation reveals that the suppression of chaos arises primarily from strain-mediated alignment dynamics rather than direct buoyancy coupling. (AA) results provide a quantitative characterization of predictability and uncertainty growth in stratified turbulence and highlight the utility of decorrelator-based methods for anisotropic geophysical flows. >>

Mrinal Jyoti Powdel, Samriddhi Sankar Ray. Uncertainty growth in stably stratified turbulence. Phys. Rev. Fluids 11, 064615. Jun 23, 2026. 

https://journals.aps.org/prfluids/abstract/10.1103/xblr-vpl3

arXiv: 2512.05656v1 [physics.flu-dyn].

https://arxiv.org/abs/2512.05656

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

Keywords: gst, chaos, turbulence, transitions, uncertainty growth, three-dimensional turbulence, stratified turbulence, infinitesimal perturbations, stratification strength, anisotropy. 

# 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: 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: 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: 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 different degrees of decimation, reduction of triadic interactions suppresses intermittency and anomalous dissipation in turbulence.

<< ️(AA) investigate how the defining statistical features of three-dimensional turbulence respond to systematic reductions of the Fourier-space triadic interaction network. Using direct numerical simulations of both fractally and homogeneously decimated Navier-Stokes dynamics, (They) show that progressive thinning of the set of active modes leads to a systematic suppression of intermittency and, most strikingly, to the vanishing of the mean dissipation rate in the large-Reynolds-number limit. >>

<< ️Structure-function exponents collapse onto their dimensional values, the multifractal singularity spectrum contracts, and the analyticity width extracted from the exponential spectral tail increases monotonically with decimation-each indicating a substantial regularization of the velocity field. >>

<< ️Together, these results provide direct evidence that anomalous dissipation in incompressible turbulence is not a generic property of the Navier-Stokes equations, but instead requires the full combinatorial richness of their triadic nonlinear interactions. >>

Anikat Kankaria, Ritwik Mukherjee, Sugan Durai Murugan, et al. Reduction of triadic interactions suppresses intermittency and anomalous dissipation in turbulence. arXiv: 2603.19180v1 [physics.flu-dyn]. Mar 19, 2026.

https://arxiv.org/abs/2603.19180

Also: turbulence, intermittency, dissipation, singularity, collapse, transition, network, in https://www.inkgmr.net/kwrds.html 

Keywords: gst, turbulence, three-dimensional turbulence, incompressible turbulence, intermittency, dissipation, anomalous dissipation, singularity, multifractal singularity spectrum contracts, collapse, transitions, networks, triadic interactions, progressive thinning, decimation.

# gst: apropos of flows of hyperpycnal river plumes

<< ️The flow of a hyperpycnal river plume into a lake with a sloping bed and without any lateral confinement is a common occurrence in nature. A characteristic example of such geophysical fluid flow system is the inflow of river Rhone in Llake Geneva. >>

<< ️In this work, (AA) study the near-field plunging dynamics of an unconfined hyperpycnal plume at laboratory scale, over an idealized bed, with a slope that is similar to the one of the natural system. The study is based on large-eddy simulation of the Navier-Stokes equations in the Boussinesq approximation. (They) focus on the effect of varying the inflow conditions and in particular the densimetric Froude number, Fr_𝑑, which is the nondimensional parameter describing the ratio between inertial and buoyancy forces acting on the plume. >>

<< ️Three simulations were performed at different values of Fr_𝑑, within the range encountered in the natural system. Similarly to previous works, (They) are able to identify lateral slumping as the main mechanism that leads to plunging of the dense river water and the formation of the characteristic triangular pattern at the lake surface. (They) are able to further identify the formation of a wake downstream of the vertex plunge point, due to the transport of mixed river-ambient water from the converging mixing layers across the plunge curve on both sides of the plume. >>

<< ️The extent of both the wake and the overall plunge region increases significantly with increase of Fr_𝑑. This mechanism can be associated to the changes of the surface patterns of the plume observed in the field. In addition, (AA) compute the total entrainment, 𝐸, of ambient lake water as the streamwise increase of volumetric flow rate downstream of the river mouth. 𝐸 is found to increase with distance from the mouth, as the plume continuously entrains ambient lake water. >> 

<< (They) find that for the same distance from the river mouth, 𝐸 is larger for lower Fr_𝑑. This increase of 𝐸 with decreasing Fr_𝑑 is attributed to two mechanisms. First, in the plunge region, lower Fr_𝑑 leads to greater lateral spread and therefore increased interface area between plume and ambient water. Second, in the underflow region, lower Fr_𝑑 results in higher mean streamwise plume velocity, enhancing entrainment intensity. >>

Georgios Giamagas, Cyrille Bonamy, Koen Blanckaert, et al. Plunging and entrainment dynamics of an unconfined hyperpycnal plume over a sloping bed. Phys. Rev. Fluids 11, 033801. Mar 5, 2026.

https://journals.aps.org/prfluids/abstract/10.1103/41p1-sn3p

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

Keywords: gst, vortex, vortices, transitions, unconfined hyperpycnal plume, lateral confinements, near-field plunging dynamics, inertial and buoyancy forces, lateral slumping, wake downstream of the vertex plunge point, lateral spread, streamwise plume velocity.

# brain: entraining chimeras, the effect of driving with regular, irregular, and real-world phases.

<< ️Chimera states in coupled oscillator networks are paradigmatic examples of partial synchronization in nonlinear systems, with direct relevance to real-world network dynamics, such as neuronal dynamics. Since real-world networks are not isolated, but embedded in larger interacting systems, chimeras have also been studied under the influence of other networks and external signals. In particular, most prior work has treated periodic forcing of chimeras in the thermodynamic limit. >>

<< ️As a consequence, it remains unclear how chimera states respond to external driving in finite-size networks, where they can spontaneously collapse into full synchronization. It is also largely unknown how realistic noisy drivers, rather than periodic signals, affect driver-response synchronization. >>

<< ️To address these open questions, (AA) drive a finite-size oscillator network that exhibits a chimera state with constant-angular-frequency phases and with the same phases superimposed with noise. (They) find that, for a specific range of angular-frequency mismatch and driving strength, (They) can entrain chimeras without causing them to collapse into full synchronization. Adding noise, in turn, reduces entrainment and facilitates collapses. >>

<< ️As a real-world application of the driven chimera state framework, (AA) also drive chimeras with phases from focal and nonfocal electroencephalography (EEG) signals recorded during seizure-free periods in patients with epilepsy. (They) observe that focal signals yield higher entrainment power, within-network coherence, and collapse power than nonfocal signals when the driver EEG's dominant frequency is close to the chimera's mean angular frequency. Away from this regime, nonfocal signals yield higher values of all three measures. The observed differences not only characterize focal and nonfocal signals, but may also provide additional insight into the seizure-free brain dynamics of epilepsy patients. >>

<< ️In conclusion, beyond quantifying how external driving signals, with or without noise, affect the dynamics of chimera states that can collapse into full synchronization, this (AA) work further bridges the study of chimera states and epilepsy research. >>

Jacopo Epifanio, Martin Brešar, Ralph G. Andrzejak. Entraining chimeras: The effect of driving with regular, irregular, and real-world phases. Phys. Rev. E 113, 034214. Mar 13, 2026.

https://journals.aps.org/pre/abstract/10.1103/vczh-r59d

Also: brain, chimera, noise, transition, collapse, network, in https://www.inkgmr.net/kwrds.html 

Keywords: gst, brain, chimeras, noise, transitions, collapse, networks, coupled oscillator networks, epilepsy, synchronization, driver-response synchronization. 

# gst: fractals in rate-induced tipping.

<< ️When parameters of a dynamical system change sufficiently fast, critical transitions can take place even in the absence of bifurcations. This phenomenon is known as rate-induced tipping and has been reported in a variety of systems, from simple ordinary differential equations and maps to mathematical models in climate sciences and ecology. In most examples, the transition happens at a critical rate of parameter change, a rate-induced tipping point, and is associated with a simple unstable orbit (edge state). >>

<< ️In this work, (AA) show how this simple picture changes when non-attracting fractal sets exist in the autonomous system, a ubiquitous situation in non-linear dynamics. (They) show that these fractals in phase space induce fractals in parameter space, which control the rates and parameter changes that result in tipping. (They) explain how such rate-induced fractals appear and how the fractal dimensions of the different sets are related to each other. >>

<< ️(AA) illustrate (Their) general theory in three paradigmatic systems: a piecewise linear one-dimensional map, the two-dimensional Hénon map, and a forced pendulum. >>

Jason Qianchuan Wang, Yi Zheng, Eduardo G. Altmann. Fractals in rate-induced tipping. arXiv: 2601.16373v1 [nlin.CD]. Jan 23, 2026.

https://arxiv.org/abs/2601.16373

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

Keywords: gst, transitions, pendulum, forced pendulum, fractals, absence of bifurcations, rate-induced tipping, criticality.

# gst: anisotropic active Brownian particle in two dimensions under stochastic resetting.

<< ️(AA) study the dynamical behavior of an anisotropic active Brownian particle subjected to various stochastic resetting protocols in two dimensions. The motion of shape-asymmetric active Brownian particles in two dimensions leads to anisotropic diffusion at short times, whereas rotational diffusion causes the transport to become isotropic at longer times. >>

<< ️(They) have considered three different resetting protocols: (1) complete resetting, when both position and orientation are reset to their initial states, (2) only the position is reset to its initial state, and (3) only orientation is reset to its initial state. >>

<< ️(They) reveal that orientational resetting sustains anisotropy even at late times. When both the spatial position and orientation are subject to resetting, a complex position probability distribution forms in the steady state. This distribution is shaped by factors such as the initial orientation angle, the anisotropy of the particle, and the resetting rate. >>

<< ️When only the translational degrees of freedom are reset, while the particle's orientation evolves naturally, the steady state no longer depends on particle asymmetry. In contrast, if only the orientation is reset, the long-term probability distribution becomes Gaussian, using an effective diffusion tensor—containing nondiagonal elements—defined by the resetting rate. More broadly, the interaction between translational and rotational dynamics, in combination with stochastic resetting, produces distinct behaviors at late times that are absent in symmetric particles. >>

<< ️Given recent progress in experimental resetting techniques, these (AA) results could be highly useful for controlling asymmetric active colloids, such as in self-assembly applications. >>

Anirban Ghosh, Sudipta Mandal, Subhasish Chaki. Anisotropic active Brownian particle in two dimensions under stochastic resetting. Phys. Rev. E 113, 014142. Jan 29, 2026.

https://journals.aps.org/pre/abstract/10.1103/11f6-srsx

arXiv: 2501.05149v2 [cond-mat.stat-mech]. Nov 25, 2025. 

https://arxiv.org/abs/2501.05149

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

Keywords: gst, particle, self-assembly, stochastic resetting.

# gst: wrinkling dynamics accelerate due to sudden changes in boundary conditions.

<< ️(AA) investigate the wrinkling dynamics of a long, flat filament immersed in a viscous fluid subjected to compression at a constant rate. Typical wrinkling dynamics proceed through three stages: initiation, development, and relaxation. The first stage, during which high mode perturbations increase exponentially while the shape and filament tension remain almost unchanged, is notably longer in the linear and nonlinear simulations than in the experiments by Chopin et al. [Phys. Rev. Lett. 119, 088001 (2017)]. >>

<< ️(AA) propose that sudden environmental changes introduce extra high-frequency perturbations beyond thermal fluctuations, which significantly accelerates the first stage. This effect is universal and inevitable for similar processes given the experimental conditions. >>

<< ️Finally, (They) analyze the relationship between the initial perturbations and the duration of the first stage. >>

Kai Liu, Wang Xiao, John Lowengrub, et al. Wrinkling dynamics accelerate due to sudden changes in boundary conditions. Phys. Rev. E 113, 015102. Jan 13, 2026.

https://journals.aps.org/pre/abstract/10.1103/18yj-mqqz

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

Keywords: gst, transitions, wrinkling

# gst: chimera states in wheel networks

<< ️How higher-order interactions influence dynamical behavior in networks of coupled chaotic oscillators remains an open question. To address this, (AA) investigate emergent dynamical behaviors in a wheel network of Rössler and Lorenz oscillators that incorporates both pairwise (1-simplex) and higher-order (2-simplex) interactions under three coupling schemes, namely, diffusive, conjugate, and mean-field diffusive coupling. >>

<< ️(AA) numerical analysis reveals four distinct collective behaviors: synchronization, desynchronization, chimera states, and synchronized clusters. To systematically classify these dynamical behaviors, (They) introduce two statistical measures that effectively capture synchronization patterns among arbitrarily positioned nodes. Applying these measures across all dynamical models and coupling schemes (six different models in total), (They) show that both pairwise and higher-order interactions crucially influence the emergence and robustness of chimera states. (They) observe that under pairwise interaction alone, chimera states appear with high prevalence in specific coupling ranges, though the robustness depends on both the coupling scheme and the underlying dynamical system. >>

<< Incorporation of higher-order interactions reveals that the higher-order interaction underlying diffusive coupling enhances chimera states in both Rössler and Lorenz networks; under conjugate coupling, it strengthens chimera states in Lorenz but instead promotes full synchronization in Rössler; and under mean-field diffusive coupling, higher-order interactions generally favor synchronization, particularly for Rössler oscillators, but promote chimera in the Lorenz system for the intermediate range of its strengths. >>

<< ️Overall, (AA) results demonstrate that higher-order interactions can significantly modulate, promote, or suppress chimera states depending on the coupling mechanism and oscillator dynamics. >>

Ashwathi Poolamanna, Medha Bhindwar, Chandrakala Meena. Chimera States in Wheel Networks. arXiv: 2601.01411v1 [nlin.CD]. Jan 4, 2026.

https://arxiv.org/abs/2601.01411

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

Keywords: gst, chimera, network, transitions

# gst: compressed self-avoiding walks in two and three dimensions.

<< ️(AA) consider the phase transition induced by compressing a self-avoiding walk in a slab where the walk is attached to both walls of the slab in two and three dimensions, and the resulting phase once the polymer is compressed. The process of moving between a stretched situation where the walls pull apart to a compressed scenario is a phase transition with some similarities to that induced by pulling and pushing the end of the polymer. >>

<< ️However, there are key differences in that the compressed state is expected to behave like a lower dimensional system, which is not the case when the force pushes only on the end point of the polymer. (They) use scaling arguments to predict the exponents both associated with the phase transition and in the compressed state and find good agreement with Monte Carlo simulations. >>

C. J. Bradly, N. R. Beaton, A. L. Owczarek. Compressed self-avoiding walks in two and three dimensions. Phys. Rev. E 112, 054126. Nov 17, 2025.

https://journals.aps.org/pre/abstract/10.1103/wtrv-4g4h

arXiv: 2506.11433v2 [cond-mat.stat-mech]. Oct 23, 2025.

https://arxiv.org/abs/2506.11433

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

Keywords: gst, transitions, phase transitions, self-avoiding walk, criticality, polymer conformation, topology.