#gst: intermittent motility of a synthetic active particle in changing environments.

<< ️(AA) experimentally investigate the dynamics of synthetic active particles composed of gravitationally bouncing, superwalking droplets confined within an annular fluid bath. >>

<< ️Driven by a topologically pumping dual-frequency waveform, the droplets exhibit alternating active (walking) and dormant (bouncing) phases, producing intermittent azimuthal motion. Tracking individual droplets reveals pseudolaminar chaotic dynamics in the time series of particle's angular position, characterized by laminar plateaus that are interrupted by short irregular bursts of activity. >>

<< ️Increasing the driving amplitude induces a qualitative change in the active particle's intermittent dynamics, arising from a symmetry-breaking transition in its Faraday-wave field environment: continuous SO(2)-symmetric "channelling" waves give way to discrete "trapping" patterns. >>

<< ️These findings demonstrate how environmental symmetry and spatiotemporal structure modulate motility and intermittency in synthetic active matter. >>

Rudra Sekhri, Rahil N. Valani, Tapio Simula. Intermittent Motility of a Synthetic Active Particle in Changing Environments. arXiv: 2512.16135v1 [physics.flu-dyn]. Dec 18, 2025.

https://arxiv.org/abs/2512.16135 

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

Keywords: gst, active matter, drops, droplets, droploids, intermittency, behavior, active walking phase, dormant bouncing phase,  trapping patterns.

# brain: abrupt over gradual learning in the differential reinforcement of response duration task.

<< ️Learning can occur in markedly different ways: in some cases, it unfolds as a gradual process, with behavior improving slowly toward an asymptotic level of performance; in others, it appears as an abrupt process that sharply separates behavior before and after a change point. Under-standing the behavioral and neural processes underlying these distinct acquisition patterns may be critical for elucidating the basic principles of learning. >>

<< ️(AA) investigated this question experimentally using naïve rats performing a differential reinforcement of response duration (DRRD) task, in which animals were required to remain inside a nosepoke for a minimum duration of 1.5 seconds to get a sugar pellet as a reward. All rats learned to wait longer in the nosepoke when comparing behavior at the beginning and at the end of the experiment. (They) tested several continuous models against a single change point (CP) model, in which behavior changes at a specific moment and remains stable thereafter. Instead of the traditional approach based on trial-segmented behavior, (AA) used the real time elapsed since the beginning of the experiment as a continuous, uncontrolled variable. (They) fitted all models to data from individual rats and compared model fit quality across alternatives. >>

<< ️(AA) results provide strong evidence in favor of an abrupt change, as captured by the CP model, over all other models. Moreover, the residuals of the CP model exhibited a Gaussian distribution, suggesting that no additional systematic dynamics remained unexplained and that the behavioral dynamics were fully captured by a single change point. >>

Mateus Gonzalez de Freitas Pinto, Alexei Magalhães Veneziani, Marcelo Bussotti Reyes. Evidence in favor of abrupt over gradual learning in the differential reinforcement of response duration (DRRD) task. bioRxiv. doi: 10.64898/ 2025.12.26.696617. Dec 27, 2025.

https://www.biorxiv.org/content/10.64898/2025.12.26.696617v1

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

Keywords: brain, behavior, cognition, learning, change point models, criticality.

# gst: settling dynamics of an oloid, experiments and simulations.

<< ️This (AA) study presents a combined experimental and computational investigation of an oloid shaped particle settling in a quiescent fluid. The oloid, a unique convex shape with anisotropic geometry, provides a distinctive model for exploring how a particle's shape and orientation affect its settling dynamics. >>

<< ️(AA) results indicate two distinct falling modes for the oloid, separated by Galileo number. The stable mode is characterised by a preferential orientation, with a rotation around the vertical axis, whereas the tumbling mode has randomly distributed orientation and rotation statistics. (They) characterise the falling velocity, orientation, and rotation dynamics of the oloids over a range of Galileo numbers. Additionally, the influence of the initial orientation is revealed to determine the rotation dynamics at low Galileo numbers. >>

Mees M. Flapper, Giulia Piumini, Roberto Verzicco, et al. Settling dynamics of an oloid: experiments and simulations. arXiv: 2511.05137v1 [physics.flu-dyn]. Nov 7, 2025.

https://arxiv.org/abs/2511.05137

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

Keywords: gst, particle, transitions, oloids, oloid shaped particles, multiple falling regimes, falling mode, tumbling mode.

# gst: synchronization by degenerate noise.

<< ️In this paper, (AA) derive several criteria for (weak) synchronization by noise without the global swift transitivity property. (Their) sufficient conditions for (weak) synchronization are necessary and can be applied to scenarios involving degenerate or non-Gaussian noise. >>

<< ️These (AA) results partially answer the open question posed by Flandoli et al. (Probab Theory Relat Fields 168:511-556, 2017). As an application, (AA) prove that the weak attractor for stochastic Lorenz 63 systems driven by degenerate noise consists of a single random point provided the noise intensity is small, and there is no weak synchronization if the noise intensity is large. This indicates that a bifurcation occurs in relation to the intensity of the noise. >>

Xianming Liu, Xu Sun. Synchronization by degenerate noise. arXiv: 2512.18278v1 [math.DS]. Dec 20, 2025.

https://arxiv.org/abs/2512.18278

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

Keywords: gst, noise, randomness, degenerate noise, non-Gaussian noise, weak synchronization, weak attractors.

# gst: triadic instabilities of internal wave standing modes.

<< ️This (AA) article presents (their) experimental study of the nonlinear destabilization of an internal wave standing mode in a uniformly stratified fluid within a rectangular domain. (They) measure the linear response of the system and target its resonances to generate a high-amplitude standing mode, prone to instabilities. Using modal decomposition tools, (They) determine the characteristics of the secondary waves and show that they have a standing-mode spatial structure. Box resonance conditions associated with nonlinear resonance conditions lead to a significant deviation from the internal wave dispersion relation and complex nonlinear interaction dynamics. >>

<< Following previous work, (AA) develop a weakly nonlinear analysis to understand the secondary wave characteristics. This approach, validated by experimental results, shows that the secondary wave characteristics as well as the general nonlinear dynamics are highly sensitive to the domain geometry and to the forcing mode. >>

Julie Deleuze, Ilias Sibgatullin, Philippe Odier, Sylvain Joubaud. Triadic instabilities of internal wave standing modes. Phys. Rev. Fluids 10, 124803. Dec 8, 2025.

https://journals.aps.org/prfluids/abstract/10.1103/2pvv-wkc4

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

Keywords: gst, waves, instability.

# 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.

# gst: apropos of reversibility, dynamics of reversible plasticity in an amorphous solid.

<< ️Local rearrangements are the elements of plastic deformation in an amorphous solid. In oscillatory shear, they can switch reversibly between two distinct configurations. While these repeating relaxations are typically considered in the limit of slow driving, their dynamics is less well understood. >>

<< ️(AA) perform experiments on a colloidal amorphous solid at an oil-water interface. The rearrangement timescales we observe span at least 1 decade, with no apparent upper bound. As frequency is increased, individual rearrangements appear faster and more hysteretic, but may disappear entirely above a crossover frequency -- suggesting that in practical experiments, the slowest rearrangements may be latent. (They) show how to find the effective potential energy that reproduces a particle's frequency-dependent motion. In rare cases, this potential energy has only one minimum. >>

Zhicheng Wang, Nathan C. Keim. Dynamics of Reversible Plasticity in an Amorphous Solid. arXiv: 2512.17816v1 [cond-mat.soft]. Dec 19, 2025.

https://arxiv.org/abs/2512.17816

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

Keywords: gst, colloids, colloidal amorphous solids, repulsive particles, reversible plasticity, plastic rearrangements, oscillatory shear, bistable rearrangements, repeating relaxations, transitions, logarithmic aging, silly putty dynamics.