# gst: apropos of adaptation of simple organisms to changing environments, self-organization and memory in a disordered entity to random driving.

AA << consider self-organization and memory formation in a mesoscopic model of an amorphous solid subject to a protocol of random shear confined to a strain range ±𝜖max. (They) develop proper readout protocols to show that the response of the driven system self-organizes to retain a memory of the strain range, which can be subsequently retrieved. >>

AA << findings generalize previous results obtained upon oscillatory driving and suggest that self-organization and memory formation of disordered materials can emerge under more general conditions, such as a disordered system interacting with its fluctuating environment. Self-organization results in a correlation between the dynamics of the system and its environment, providing thereby an elementary mechanism for sensing. >>

AA << conclude by discussing (Their)  results and their potential relevance for the adaptation of simple organisms lacking a brain to changing environments. >>

Muhittin Mungan, Dheeraj Kumar, et al. Self-Organization and Memory in a Disordered Solid Subject to Random Driving. Phys. Rev. Lett. 134, 178203. April 30, 2025.

https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.134.178203

arXiv: 2409.17096v2 [cond-mat.soft]. 

https://arxiv.org/abs/2409.17096

Also: disorder & fluctuations, 

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

Keywords: gst, disorder, fluctuations, self-assembly, self-organization, transitions

# gst: inverse design of Kirigami; contracted shapes, deployed shapes, internal trajectories of rotating units.

<< Kirigami metamaterials have enabled a plethora of morphing patterns across art and engineering. However, the inverse design of kirigami for complex shapes remains a puzzle that so far cannot be solved without relying on complex numerical methods. >>

Here, AA << present a purely geometric design method to overcome the reliance on sophisticated numerical algorithms and showcase how to leverage it for three distinct types of morphing targets, i.e., the contracted shape, the deployed shape, and the internal trajectories of the rotating units in kirigami specimens. >>

AA << results unveil the fundamental relations between the kirigami deformation and the shape of its rotating units and enable us to establish the underpinning physics through theoretical investigations validated via numerical simulations. >>

Chuan Qiao, Shijun Chen, et al. Inverse Design of Kirigami through Shape Programming of Rotating Units. Phys. Rev. Lett. 134, 176103. May 2, 2025.

https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.134.176103

Also: kirigami, origami, metamorphosis,  in https://www.inkgmr.net/kwrds.html 

Keywords: gst, kirigami, origami, metamorphosis

# gst: like fireflies or neurons, dynamics of pulsating swarmalators on a ring.

AA << study a simple one-dimensional model of swarmalators, a generalization of phase oscillators that swarm around in space as well as synchronize internal oscillations in time. Previous studies of the model focused on Kuramoto-type couplings, where the phase interactions are governed by phase differences. >>

 Here AA << consider Winfree-type coupling, where the interactions are multiplicative, determined by the product of a phase response function  and phase pulse function . This more general interaction (from which the Kuramoto phase differences emerge after averaging) produces rich physics: six long-term modes of organization are found, which we characterize numerically and analytically. >>

Samali Ghosh, Kevin O'Keeffe, et al. Dynamics of pulsating swarmalators on a ring. arXiv: 2504.14912v1 [nlin.AO]. Apr 21, 2025. 

https://arxiv.org/abs/2504.14912

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

Keywords: gst, swarm, swarmalators, instability

# gst: transitions of breakup regimes for viscous droplets in airflow.

In this AA study, << the transitions of breakup regimes for viscous droplets are investigated experimentally using high-speed imaging taken from a side view and a 45 view. Based on the morphology change in the middle of the droplet, the breakup regimes are classified into no-breakup, bag breakup, bag-stamen, low-order multimode, high-order multimode, and shear-stripping breakup. The droplet morphologies in different regimes and the corresponding transitions are discussed in detail. >>

<< The droplet viscosity dissipates the kinetic energy transferred by the airflow during the initial droplet flattening, and affects the development of the Rayleigh-Taylor instability wave after the flattening. Through the analysis of the droplet deformation and the Rayleigh-Taylor instability with the droplet viscosity taken into account, the transition conditions of different regimes are obtained in a regime map. By further considering the relative velocity loss between the droplet and the airflow, the ranges of the dual-bag breakup in the low-order multimode regime and the droplet retraction in the bag-stamen regime are determined. >>

Zhikun Xu, Tianyou Wang, Zhizhao Che. Transitions of breakup regimes for viscous droplets in airflow. arXiv: 2504.14149v1 [physics.flu-dyn]. Apr 19, 2025.

https://arxiv.org/abs/2504.14149

Also: drop, droplet, droploid, transition, instability, waves, in https://www.inkgmr.net/kwrds.html 

Keywords: gst, drops, droplets, droploids, viscous droplets, droplet breakup, transitions, instability, waves

# gst: period-doubling route to chaos in viscoelastic flows

<< Polymer solutions can develop chaotic flows, even at low inertia. This purely elastic turbulence is well studied, but little is known about the transition to chaos. In two-dimensional (2D) channel flow and parallel shear flow, traveling wave solutions involving coherent structures are present for sufficiently large fluid elasticity. >>

AA << numerically study 2D periodic parallel shear flow in viscoelastic fluids, and (They) show that these traveling waves become oscillatory and undergo a series of period-doubling bifurcations en-route to chaos. >>

Jeffrey Nichols, Robert D. Guy, Becca Thomases. Period-doubling route to chaos in viscoelastic Kolmogorov flow. Phys. Rev. Fluids 10, L041301. Apr 17, 2025.

https://journals.aps.org/prfluids/abstract/10.1103/PhysRevFluids.10.L041301

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

Keywords: gst, chaos, waves, traveling waves, elasticity, viscoelastic fluids, turbulence, elastic turbulence, period-doubling bifurcations, transitions

# gst: apropos of migrations, asymmetric simple exclusion process with concerted hopping.

<< An important mechanism enabling fast ion diffusion in solid electrolytes is considered to be the significant lowering of the activation barrier when two or more ion particles hop simultaneously between sites, i.e., concerted migration, compared to single-ion hopping. >>

In this study AA << incorporate a mechanism of simultaneous particle hopping into the asymmetric simple exclusion process, which is an archetypal model for many-particle transportation phenomena, and investigate its impact on particle transport properties. >>

In Their model, << reflecting ion dynamics, the hopping rates are controlled by the activation energy, inverse temperature, and strength of an external driving field. (AA) first construct an exact solution that describes the steady state of the proposed model. By using this solution, (They) find that concerted migration substantially increases the particle current and induces a shift of the peak in the fundamental diagram, i.e., the density-current relationship. >>

AA << also show the presence of a critical temperature that maximizes the current. Additionally, we discuss the implications within parameter regions corresponding to actual materials. >>

Takahiro Ezaki, Kai Kihara, et al. Asymmetric simple exclusion process with concerted hopping. Phys. Rev. Research 7, 023068. Apr 21, 2025.

https://journals.aps.org/prresearch/abstract/10.1103/PhysRevResearch.7.023068

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

Keywords: gst, particles, migration, asymmetric exclusion process, hopping, hopping rates

# gst: homology for structural characterization in disordered systems

<< Local and global structural characterizations emphasize different aspects of materials, with the former focusing on microscopic features like coordination environment, short-range order, bond angles and lengths, and the latter on macroscopic features like long-range order, phase structure, lattice constants, and overall symmetry. In conclusion, local characterization focuses on the environment and structure of individual particles or regions, while global characterization refers to the overall topology or geometry of the material. >>

AA << propose a unified framework based on persistent homology to characterize both local and global structures in disordered systems. It can simultaneously generate local and global descriptors using the same algorithm and data structure, and has been shown to be highly effective and interpretable in predicting particle rearrangements and classifying global phases. >>

AA also << define a nonparametric metric, the separation index, (that) establishes a connection between particle environments and the global phase structure. >>

An Wang, Li Zou. Persistent homology for structural characterization in disordered systems. Phys. Rev. E 111, 045306. Apr 17, 2025.

https://journals.aps.org/pre/abstract/10.1103/PhysRevE.111.045306

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

Keywords: gst, particle, disorder, homology