# gst: geometry of contraction-induced flows.

<< ️Peristalsis is the driving mechanism behind a broad array of biological and engineered flows. In peristaltic pumping, a wavelike contraction of the tube wall produces local changes in volume which induce flow. Net flow arises due to geometric nonlinearities in the momentum equation, which must be properly captured to compute the flow accurately. >>

<< ️While most previous models focus on radius-imposed peristalsis, they often neglect longitudinal length changes—a natural consequence of radial contraction in elastic materials. In this paper, to capture a more accurate picture of peristaltic pumping, (AA) calculate the flow in an elastic vessel undergoing contractions in the transverse and longitudinal directions simultaneously, keeping the geometric nonlinearities arising in the strain. >>

<< ️(They) demonstrate that transverse and longitudinal contractions induce instantaneous flows at the same order in wall strain but in opposite directions. (They) investigate the influence of the wall's Poisson ratio on the flow profile. Incompressible walls suppress flow by minimizing local volume changes, whereas auxetic walls enhance flow. For radius-imposed peristaltic waves, wall incompressibility reduces both reflux and particle trapping. In contrast, length-imposed waves typically generate backflow, although trapping can still occur at large amplitudes for some Poisson ratios. >>

Aaron Winn, Eleni Katifori. Geometry of contraction-induced flows. Phys. Rev. Fluids 11, 033101. Mar 12, 2026.

https://journals.aps.org/prfluids/abstract/10.1103/pw9s-vvf4

arXiv: 2510.24016v1 [physics.flu-dyn]. Oct 28, 2025.

https://arxiv.org/abs/2510.24016

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

Keywords: gst, waves, elasticity, networks, peristalsis, peristaltic pumping, peristaltic waves, wavelike contractions, transverse and longitudinal contractions, longitudinal length changes, instantaneous flows, auxetic walls, backflows.

# gst: from fluttering to drifting: inertialess sedimentation of an achiral particle.

<< ️There has been much recent interest in the chiral motion of achiral particles that sediment in a viscous fluid in a regime where inertial effects can be neglected. This occurs in a broad range of applications such as those involving biological objects like algae, ultrathin graphene flakes, or colloidal suspensions. It is known that particles with two planes of symmetry can be categorized as “settlers,” “drifters,” or “flutterers,” where the latter sediment along chiral trajectories despite their achiral shapes. >>

<< ️Previous work investigated the sedimentation of circular disks bent into a U-shape and identified them as “flutterers.” In this work (AA) analyze the change in behavior of such particles when (They) break one of their symmetries by pinching the disks isometrically along their axis, a shape change that can arise during the sedimentation of thin elastic sheets. The “fluttering” behavior is found to be robust to such shape changes, with the trajectories now evolving toward helical paths. However, the behavior changes when the degree of pinching becomes too strong, at which point the particles become “drifters” which sediment steadily without rotation. >>

<< ️(AA) establish criteria for the transition between the two types of behavior and confirm (Their) predictions in experiments. Finally, (AA) discuss the implications of (Their) observations for the dispersion of dilute suspensions made of such particles. >>

Christian Vaquero-Stainer, Tymoteusz Miara, Anne Juel, et al. From fluttering to drifting: Inertialess sedimentation of an achiral particle. Phys. Rev. Fluids 11, 034102. March 10, 2026.

https://journals.aps.org/prfluids/abstract/10.1103/scj8-6lpf

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

Keywords: gst, behaviors, particles, achiral particles, settlers, drifters, flutterers.

# gst: prolate and oblate nematic shells under equal and hybrid alignments.

<< ️Using the Landau–de Gennes free-energy formalism with the fast inertial relaxation engine relaxation method, (AA) investigate the role of geometry and anchoring conditions in nematic liquid crystal shells. Both prolate and oblate geometries are explored for four distinct anchoring configurations: degenerate planar on both surfaces, homeotropic on both surfaces, and hybrid cases with planar-homeotropic and homeotropic-planar alignments. (Their) simulations reveal a rich variety of topological defect arrangements, including bipolar configurations with boojums; tetrahedral patterns featuring disclination lines, boojums, and hedgehogs; Saturn-ring structures; and twisted director fields in the equatorial plane. >>

<< ️Detailed energy analyses demonstrate that elastic distortions—splay, bend, and twist—are strongly influenced by parameters such as inner and outer radii, shell thickness, and aspect ratio, which in turn dictate the stabilization of specific defect structures. ️These findings provide insights into the curvature-driven mechanisms that control the formation of defects in nematic shells. >>

F. C. Cruz, E. K. Lenzi, Q. Li, et al. Prolate and oblate nematic shells under equal and hybrid alignments. Phys. Rev. E 113, 035403. Mar 4, 2026.

https://journals.aps.org/pre/abstract/10.1103/3ynk-2nsp

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

Keywords: gst, spheroids, elasticity, nematic liquid crystal shells, prolate and oblate geometries, topological defects, elastic distortions, curvature-driven mechanisms.

# gst: predicting oscillations in complex networks with delayed feedback.

<< ️Oscillatory dynamics are common features of complex networks, often playing essential roles in regulating function. Across scales from gene regulatory networks to ecosystems, delayed feedback mechanisms are key drivers of system-scale oscillations. >> 

<< ️The analysis and prediction of such dynamics are highly challenging, however, due to the combination of high-dimensionality, non-linearity and delay. Here, (AA) systematically investigate how structural complexity and delayed feedback jointly induce oscillatory dynamics in complex systems, and introduce an analytic framework comprising theoretical dimension reduction and data-driven prediction. >>

<< ️(They) reveal that oscillations emerge from the interplay of structural complexity and delay, with reduced models uncovering their critical thresholds and showing that greater connectivity lowers the delay required for their onset. (Their) theory is empirically tested in an experiment on a programmable electronic circuit, where oscillations are observed once structural complexity and feedback delay exceeded the critical thresholds predicted by our theory. >>

<< ️Finally, (They) deploy a reservoir computing pipeline to accurately predict the onset of oscillations directly from timeseries data. (AA) findings deepen understanding of oscillatory regulation and offer new avenues for predicting dynamics in complex networks. >>

Shijie Liu, Jinliang Han, Jianming Liu, et al. Predicting oscillations in complex networks with delayed feedback. arXiv: 2603.04251v2 [cond-mat.dis-nn]. Mar 4, 2026.

https://arxiv.org/abs/2603.04251

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

Keywords: gst, networks, oscillatory dynamics, oscillatory regulations, system-scale oscillations, delay, delayed feedback mechanisms, criticality, critical thresholds.

# gst: localization of information driven by stochastic resetting.

<< ️The dynamics of extended many-body systems are generically chaotic. Classically, a hallmark of chaos is the exponential sensitivity to initial conditions captured by positive Lyapunov exponents. Supplementing chaotic dynamics with stochastic resetting drives a sharp dynamical phase transition: (AA) show that the Lyapunov spectrum, i.e., the complete set of Lyapunov exponents, abruptly collapses to zero above a critical resetting rate. >>

<< ️At criticality, (They) find a sudden loss of analyticity of the velocity-dependent Lyapunov exponent, which (They) relate to the transition from ballistic scrambling of information to an arrested regime where information becomes exponentially localized over a characteristic length diverging at criticality with an exponent 𝜈=1/2 and a dynamical exponent 𝑧=2. (They) illustrate (Their) analytical results on generic chaotic dynamics by numerical simulations of coupled map lattices. >>

Camille Aron, Manas Kulkarni. Localization of information driven by stochastic resetting. Phys. Rev. E 113, L022101. Feb 23, 2026.

https://journals.aps.org/pre/abstract/10.1103/pkgb-mp8s

arXiv:2510.07394v2 [cond-mat.stat-mech]. Feb 24, 2026.

https://arxiv.org/abs/2510.07394

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

Keywords: gst, chaos, transition, collapse, randomness, stochasticity, stochastic resetting, phase transition, criticality, critical resetting rate, ballistic scrambling of information.

# sound: screeching sound of peeling tape.

<< ️The screeching of peeling tape is a familiar albeit annoying sound. However, despite decades of study, its source has remained elusive. Herein (AA) demonstrate that this sound is produced by a discrete train of weak shocks emanating from the fine fractures which travel supersonically with respect to the surrounding air, in the transverse direction within the detaching adhesive. >>

<< ️Each sound pulse is generated when a fracture tip reaches the edge of the tape. (They) verify this using two microphones synchronized with clips from two simultaneous high-speed video cameras, one observing the fracture motions in the adhesive through the transparent substrate, while the other captures schlieren imaging of the shock fronts in the air. >>

Er Qiang Li, Paul W. Riker, Sriram Rengarajan, et al. Screeching sound of peeling tape. Phys. Rev. E 113, 025508. Feb 24, 2026.

https://journals.aps.org/pre/abstract/10.1103/p19h-9ysx

Also: sound, noise, fracture, crack, jazz, in https://www.inkgmr.net/kwrds.html 

Keywords: sound, noise, fracture, crack, screeching, discrete train of weak shocks, jazz

# brain: collective dynamics in spiking neural networks beyond Dale's principle.

<< ️Dale's Principle has historically guided neuroscience research as a valuable rule of thumb, namely that all synapses on each neuron release the same set of neurotransmitters. Most existing Spiking Neuron Network models share this dichotomous assumption that neurons are either excitatory or inhibitory; however, recent experimental evidence points towards co-release mechanisms that violate this assumption. >>

<< ️Here, (AA) introduce a minimal model of "Bilingual" neurons violating Dale's principle that can exert both excitatory and inhibitory effects. (They) identify parameter regimes in which this architecture exhibits transitions between synchronous and asynchronous dynamics that differ quantitatively from those observed in a matched monolingual control architecture. >>

<< ️(AA) report distinct information-processing signatures both at the level of neurons and higher-order interactions between them near the phase transitions. These (AA) results suggest that the population of neurons violating Dale's principle may provide an alternative mechanism for regulating large-scale oscillatory activity in neural circuits. >>

Ross Ah-Weng, Hardik Rajpal. Collective Dynamics in Spiking Neural Networks Beyond Dale's Principle. arXiv: 2602.23202v1 [q-bio.NC]. Feb 26, 2026.

https://arxiv.org/abs/2602.23202

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

Keywords: gst, brain, neuro, networks, transitions, neural circuits, spiking neuron networks, excitatory and inhibitory effects, Dale's principle, Henry Hallett Dale, bilingual neurons, transitions between synchronous and asynchronous dynamics.