# gst: stability of twisted states; the role of phase lag, pairwise and higher-order interactions.

<< ️Stability analysis remains a key focus in the nonlinear field. The stability of oscillator networks considering phase-lag coupling is still an unsolved puzzle. Here, (AA)  investigate the linear stability using the maximal Lyapunov exponent and evaluate the basin stability by numerical simulations. >>

<< ️The results show that the phase lag has no significant effect on the proportion of twisted states with linear stability and on their basin sizes, without considering higher-order interactions. In contrast to the stabilizing effect of higher-order interactions on twisted states, pairwise coupling suppresses their linear stability but enhances their basin stability. >>

<< ️When pairwise coupling dominates, phase lag acts to strengthen the linear stability of the twisted state. Furthermore, the phase lag reduces the degree of ordering of the system and shrinks the basin of the twisted state. >>

<< ️These results highlight the synergistic effect of phase lag with pairwise and higher-order interactions on twisted-state basins. >>

Xueqin Wang, Dong Yu, et al. Stability of twisted states: The role of phase lag, pairwise and higher-order interactions. Phys. Rev. E 112, 024202. Aug 1, 2025.

https://journals.aps.org/pre/abstract/10.1103/qmgz-h5qm

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

Keywords: gst, network, chimera, phase lags, pause, coupled oscillators, synchronization.

# gst: nonreciprocal coupling triggers pinning-depinning transitions of wavefronts in bistable systems chains.

<< ️Coupled discrete systems with reciprocal and nonreciprocal couplings exhibit unexpected and counterintuitive phenomena compared to continuous systems. (AA) investigate the pinning-depinning transition induced by nonreciprocal coupling in nonlinear wave propagation connecting different equilibria in bistable system chains. >>

Experimentally, their system << ️exhibits the propagation of fronts between homogeneous states. The fronts display a pinning-depinning transition by increasing the nonreciprocal coupling, achieved by increasing optical feedback offset. Close to the bifurcation, the front velocity is characterized by a square root law as a function of the bifurcation parameter. >>

L. B. Ramirez-Moya, M. Diaz-Zuniga, et al. Nonreciprocal coupling triggers pinning-depinning transitions of wavefronts in bistable systems chains. Phys. Rev. Research 7, L032023. Aug 1, 2025.

https://journals.aps.org/prresearch/abstract/10.1103/9ypt-4kvs

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

Keywords: gst, waves, transitions, pinning-depinning transitions

# behav: make silence speak for itself.

<< ️Silence is a common phenomenon in classrooms, yet its implicit nature limits a clear understanding of students' underlying learning statuses. >>

<< ️This (AA) study proposed a nuanced framework to classify classroom silence based on class events and student status, and examined neurophysiological markers to reveal similarities and differences in silent states across achievement groups. (..) The study involved 54 middle school students during 34 math lessons, with simultaneous recordings of electroencephalogram (EEG), electrodermal activity (EDA), and heart rate signals, alongside video coding of classroom behaviors. >>

AA << found that high-achieving students showed no significant difference in mean EDA features between strategic silence (i.e., students choose silence deliberately) and active speaking during open questioning but exhibited higher EEG high-frequency relative power spectral density (RPSD) during strategic silence. In structural silence (i.e., students maintain silence following an external command) during directed questioning, they demonstrated significantly higher heart rates while listening to lectures compared to group activities, indicating heightened engagement. Both high- and medium-achieving students displayed elevated heart rates and EDA tonic components in structural silence during questioning compared to teaching. Furthermore, high-achieving students exhibited lower high-frequency RPSD during structural silence than strategic silence, a pattern not observed in other groups, highlighting group heterogeneity. >>

<< ️The (AA) findings contribute to validating the complexity of silence, challenge its traditional association with passivity, and offer a novel classification framework along with preliminary empirical evidence to deepen the understanding of silent learning behaviors in classroom contexts. >>

Mingxuan Gao, Jingjing Chen, et al. Make Silence Speak for Itself: a multi-modal learning analytic approach with neurophysiological data. arXiv: 2507.21063v1 [q-bio.NC]. May 23, 2025.

https://arxiv.org/abs/2507.21063

Also: silence, pause, behav, brain, in https://www.inkgmr.net/kwrds.html 

Keywords: behavior, brain, pause, silence, strategic silence, structural silence

# gst: fluctuations around turbulence

<< ️Numerical simulations of turbulent flows at realistic Reynolds numbers generally rely on filtering out small scales from the Navier Stokes equations and modeling their impact through the Reynolds stress tensor τ_ij. Traditional models approximate τ_ij solely as a function of the filtered velocity gradient, leading to deterministic subgrid scale closures. However, small scale fluctuations can locally exhibit instantaneous values whose deviation from the mean can have a significant influence on flow dynamics. >>

<< ️In this work, (AA) investigate these effects by employing direct numerical simulations combined with Gaussian filtering to quantify subgrid scale effects and evaluating the local energy flux in both space and time. The mean performance of the canonical Clark model is assessed by conditioning the energy flux distributions on the invariants of the filtered velocity gradient tensor, Q and R. The Clark model captures to a good degree the mean energy flux. However, the fluctuations around these mean values for given (Q, R) are of the order of the mean displaying fat tailed distributions. ️To become more precise, (AA) examine the joint distributions of true energy flux and the predictions from both the Clark and the Smagorinsky models. >>

<< ️This approach mirrors the strategy adopted in early stochastic subgrid scale models. Clear non Gaussian characteristics emerge from the obtained distributions, particularly through the appearance of heavy tails. The mean, the variance, the skewness and flatness of these distributions are quantified. (Their) results emphasize that fluctuations are an integral component of the small scale feedback onto large scale dynamics and should be incorporated into subgrid scale modeling through an appropriate stochastic framework. >>

Flavio Tuteri, Alexandros Alexakis, Sergio Chibbaro. Fluctuations around Turbulence Models. arXiv: 2507.17575v1 [physics.flu-dyn]. Jul 23, 2025. 

https://arxiv.org/abs/2507.17575

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

Keywords: gst, disorder & fluctuations, turbulence.

# gst: an analysis of the phenomenon of chaotic itinerancy.

AA << introduce a new methodology for the analysis of the phenomenon of chaotic itinerancy in a dynamical system using the notion of entropy and a clustering algorithm. (They) determine systems likely to experience chaotic itinerancy by means of local Shannon entropy and local permutation entropy. In such systems, we find quasi-stable states (attractor ruins) and chaotic transition states using a density-based clustering algorithm. >>

Their << ️approach then focuses on examining the chaotic itinerancy dynamics through the characterization of residence times within these states and chaotic transitions between them with the help of some statistical tests. The effectiveness of these methods is demonstrated on two systems that serve as well-known models exhibiting chaotic itinerancy: globally coupled logistic maps (GCM) and mutually coupled Gaussian maps. >>

<< ️Although the phenomenon of chaotic itinerancy is often associated with high dimensional systems, (They) were able to provide evidence for the presence of this phenomenon in the studied low-dimensional systems. >>

Nikodem Mierski, Paweł Pilarczyk. Analysis of the Chaotic Itinerancy Phenomenon using Entropy and Clustering. arXiv: 2507.22643v1 [nlin.CD]. Jul 30, 2025. 

https://arxiv.org/abs/2507.22643

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

Keywords: gst, chaos, intermittency, transitions, chaotic itinerancy, low-dimensional systems.

# behav: souvenir collector's walk; the distribution of the number of steps of a continuous-time random walk ending at a given position.

AA << consider a random walker performing a continuous-time random walk (CTRW) with a symmetric step lengths' distribution possessing a finite second moment and with a power-law waiting time distribution with finite or diverging first moment. The problem (They) pose concerns the distribution of the number of steps of the corresponding CTRW conditioned on the final position of the walker at some long time 𝑡. >>

<< ️For positions within the scaling domain of the probability density function (PDF) of final displacements, the distributions of the number of steps show a considerable amount of universality, and are different in the cases when the corresponding CTRW corresponds to subdiffusion and to normal diffusion. >>

They << ️moreover note that the mean value of the number of steps can be obtained independently and follows from the solution of the Poisson equation whose right-hand side depends on the PDF of displacements only. >>

<< ️This approach works not only in the scaling domain but also in the large deviation domain of the corresponding PDF, where the behavior of the mean number of steps is very sensitive to the details of the waiting time distribution beyond its power-law asymptotics. >>

Igor M. Sokolov. Souvenir collector's walk: The distribution of the number of steps of a continuous-time random walk ending at a given position. Phys. Rev. E 112, 024101. Aug 1, 2025

https://journals.aps.org/pre/abstract/10.1103/6j5n-bqcf

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

Keywords: behavior, walk, walking, random walks, randomness.

# gst: reversible switching due to attraction and repulsion: clusters, gaps, sorting, and mixing.

AA << ️describe a phase transition in continuum limits of interacting particle systems that exhibits a vertical bifurcation diagram. The transition is mediated by a competition short-range repulsion and long-range attraction. As a consequence of the transition, infinitesimal parameter variations allow switching between uniform distribution and clusters in single-species models, and between mixed and sorted states in multi-species contexts, without hysteresis. >>

Their << main technical contribution is a universal expansion for the size of vacuum bubbles that arise in this phase transition and a quantitative analysis of the effect of noise. >>

Arnd Scheel, Angela Stevens. Reversible switching due to attraction and repulsion: clusters, gaps, sorting, and mixing. arXiv: 2507.10406v1 [math.DS]. Jul 14, 2025.

https://arxiv.org/abs/2507.10406

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

Keywords: gst, particles, bubbles, noise, short-range repulsion, long-range attraction, phase transitions.