Chiral active particles are able to draw energy from the environment to self-propel in the form of rotation. We describe an experimental arrangement wherein chiral objects, spinners, floating on the surface of a vibrated fluid rotate due to emitted capillary waves. We observe that pairs of spinners can assemble at quantized distances via the mutually generated wavefield, phase synchronize and, in some circumstances, globally rotate about a point midway between them. A mathematical model based on wave-mediated interactions captures the salient features of the assembly and synchronization while a qualitative argument is able to rationalize global rotations based on interference and radiation stress associated with the wavefield. Extensions to larger collections are demonstrated, highlighting the potential for this tabletop system to be used as an experimental system capable of synchronizing and swarming.

It is shown that the Landau damping of electron plasma waves (EPWs) is significantly enhanced in a transverse magnetic field with tens of teslas due to a strong modification of the electron velocity distribution function formed in the two-plasmon-decay (TPD) process. The Landau damping even in the range of $0.1<k{\lambda }_D<0.25$ ($k$ is the wave number of EPW; ${\lambda }_D$ is the Debye length) is important. As a result, the TPD instability saturates at a lower level in the transverse magnetic field; in particular, the convective TPD is significantly suppressed. Meanwhile the laser transmission increases, and the risk of target preheating from hot electrons is also effectively diminished. In addition, the influences of magnetic fields with different strengths and directions on the evolution of TPD are investigated. The results show that as long as the magnetic field can effectively confine the hot electrons and change the electron velocity distribution function, the development of TPD can be mitigated. Finally, we directly investigate the TPD evolution in plasmas with the bi-Maxwellian distribution in order to construct the environment with an external transverse magnetic field. Due to the direct enhancement of EPW Landau damping, the development of TPD remains at a relatively low level in both its linear and nonlinear stages. This further demonstrates the importance of this nonlinear saturation mechanism of TPD in magnetized plasmas.

A detailed study of published experimental data for a variety of materials on the incremental variation of heat capacity, thermal expansion, and compressibility at glassy freezing reveals a striking dependence of the Prigogine-Defay ratio $R$ on the fragility index $m$. At high $m, R$ approaches values of $\sim 1$, the Ehrenfest expectation for second-order continuous phase transitions, while $R$ reaches values $>20$ for low fragilities. We explain this correlation by the degree of separation of the glassy freezing temperature from a hidden phase transition into an ideal low-temperature glass.

A method for simulating electrorheological (ER) fluids is developed using LAMMPS (large-scale atomic, molecular massively parallel simulator) molecular dynamics simulations, aiming to model and analyze the microstructure and rheological behavior of ER fluids under an electric field. The results demonstrate that our simulation accurately captures the microstructural changes in ER fluids, and the simulation data show an impressively high level of consistency when compared directly with experimental data. The main innovation lies in our simultaneous consideration of dipole interactions, harmonic effects of ER particles, and the contact effect of electrode plates. The contact effect model is demonstrated in detail in our simulations of the chain formation process and the shear process of ER particles in ER fluids, accompanied by corresponding experimental comparisons. Our simulations provide insights into the microscopic mechanisms of ER fluids and establish a theoretical foundation for the development of smart materials and rheological devices.

The Stokes-Einstein (SE) relation, which relates diffusion constants with the viscosity of a liquid at high temperatures in equilibrium, is violated in the supercooled temperature regime. Whether this relation is obeyed in nonequilibrium active liquids is a question of significant current interest to the statistical physics community trying to develop the theoretical framework of nonequilibrium statistical mechanics. Via extensive computer simulations of model active glass-forming liquids in three dimensions, we show that SE is obeyed at a high temperature similar to the equilibrium behavior, and it gets violated in the supercooled temperature regimes. The degree of violation increases systematically with the increasing activity which quantifies the amount the system is driven out of equilibrium. First passage-time (FPT) distributions helped us to gain insights into this enhanced breakdown from the increased short-time peak, depicting hoppers. Subsequently, we study the wave vector dependence of SE relation and show that it gets restored at a wave vector that decreases with increasing activity, and the crossover wave vector is found to be proportional to the inverse of the dynamical heterogeneity length scale in the system. Our work showed how SE violation in active supercooled liquids could be rationalized using the growth of dynamic length scale, which is found to grow enormously with increasing activity in these systems.

A monolayer transmission metasurface (MTMS) combining a radial phase shift plate (RPSP) and a spiral phase plate is developed to realize the quasiperfect fractional ultrasonic vortex (FUV). The theoretical prediction for the quasiperfect FUV generation by the MTMS has been demonstrated by numerical simulations. The MTMSs produce transmitted quasiperfect FUVs with different topological charges, which display annular distributions with a constant radius and a low-intensity gap. Additionally, it is found that the radial phase shift factor of the RPSP can effectively modify and expand the intensity ring radius of the obtained quasiperfect FUV. Finally, we fabricate the discretized MTMS, and experimentally verify that the suggested MTMS can generate the quasiperfect FUV. The quasiperfect FUV generated by the simple MTMS includes the advantages of both the fractional vortex and the perfect vortex, which may have potential applications in underwater communication, imaging, and particle manipulation.

Using a powerful combination of projection-operator method and path-space response theory, we derive the fluctuation dynamics of a slow inertial probe coupled to a steady nonequilibrium medium under the assumption of time-scale separation. The nonequilibrium is realized by external nongradient driving on the medium particles or by their (athermal) active self-propulsion. The resulting friction on the probe is an explicit time correlation for medium observables and is decomposed into two terms: one entropic, proportional to the noise variance as in the Einstein relation for equilibrium media, and a frenetic term that can take both signs. As an illustration, we give the exact expressions for the linear friction coefficient and noise amplitude of a probe in a rotating run-and-tumble medium. We find a transition to absolute negative probe friction as the nonequilibrium medium exhibits sufficient and persistent rotational current. There, the run-away of the probe to high speeds realizes a nonequilibrium-induced acceleration. Simulations show that its speed finally saturates, yielding a symmetric stationary probe-momentum distribution with two peaks.

In this paper, we study the stability of a simple model of a hyperloop vehicle resulting from the interaction between electromagnetic and aeroelastic forces for both constant and periodically varying coefficients (i.e., parametric excitation). For the constant coefficients, through linear stability analysis, we analytically identify three distinct regions for the physically significant equilibrium point. Further inspection reveals that the system exhibits limit-cycle vibrations in one of these regions. Using the harmonic balance method, we determine the properties of the limit cycle, thereby unraveling the frequency and amplitude that characterize the periodic oscillations of the system's variables. For the varying coefficients case, the stability is studied using Floquet analysis and Hill's determinant method. The part of the stability boundary related to parametric resonance has an elliptical shape, while the remaining part remains unchanged. One of the major findings is that a linear parametric force can suppress or amplify the parametric resonance induced by another parametric force depending on the amplitude of the former. In the context of the hyperloop system, this means that parametric resonance caused by base excitation—in other words by the linearized parametric electromagnetic force—can be suppressed by modulating the coefficient of the aeroelastic force in the same frequency. The effectiveness is also highly dependent on the phase difference between the modulation and the base excitation. The origin of the suppression is attributed to the stabilizing character of the parametric aeroelastic force as revealed through energy analysis. We provide analytical expressions for the stability boundaries and for the stability's dependence on the phase shift of the modulation. Finally, we emphasize that suppressing parametric resonance through an added, linear state-dependent force with the coefficient having the same period as the original force can be achieved in other physical systems too.

We calculate the maximum Lyapunov exponent of the motion in the separatrix map's chaotic layer, along with calculation of its width, as functions of the adiabaticity parameter $\lambda$. The separatrix map is set in natural variables, and the case of the layer's least perturbed border is considered, i.e., the winding number of the layer's border (the last invariant curve) is the golden mean. Although these two dependences (for the Lyapunov exponent and the layer width) are strongly nonmonotonous and evade any simple analytical description, the calculated dynamical entropy $h$ turns out to be a close-to-linear function of $\lambda$. In other words, if normalized by $\lambda$, the entropy is a quasiconstant. We discuss whether the function $h\left(\lambda \right)$ can be in fact exactly linear, $h\propto \lambda$. The function $h\left(\lambda \right)$ forms a basis for calculating the dynamical entropy for any perturbed nonlinear resonance in the first fundamental model, as soon as the corresponding Melnikov-Arnold integral is estimated.

With an increasing number of observations on the dynamics of many complex systems, it is necessary to reveal the underlying mechanisms behind these complex dynamics, which is fundamentally important in many scientific fields such as climate, financial, ecological, and neural systems. The underlying mechanisms are commonly encoded into network structures, e.g., capturing how constituents interact with each other to produce emergent behavior. Here, we address whether a good network reconstruction suggests a good dynamics prediction. The answer depends on the nature of the supplied (observed) dynamics sequences measured on the complex system. When the dynamics are not chaotic, network reconstruction implies dynamics prediction. In contrast, even if a network can be well reconstructed from the chaotic time series (chaos means that many unstable dynamics states coexist), the prediction of the future dynamics can become impossible as at some future point the prediction error will be amplified. This is explained using dynamical mean-field theory on a toy model of random recurrent neural networks.

A considerable number of semiempirical and first-principles models have been created to describe the dynamic response of a collisionally damped charged-particle system. However, known challenges persist for established dynamic structure factors (DSFs), dielectric functions, and conductivities. For instance, the semiempirical Drude-Smith conductivity [Smith, Phys. Rev. B 64, 155106 (2001)] lacks interpretability, and the first-principles Mermin dielectric function [Mermin, Phys. Rev. B 1, 2362 (1970)] does not satisfy the frequency sum rule [Atwal and Ashcroft, Phys. Rev. B 65, 115109 (2002)]. In this work, starting from the multicomponent Bhatnagar-Gross-Krook (BGK) kinetic equation, we produce a multispecies susceptibility that conserves number and momentum, which we refer to as the completed Mermin susceptibility, and we explore its properties and uses. We show that the completed Mermin susceptibility satisfies the frequency sum ($f$-sum) rule. We compute the associated DSF and find that momentum conservation qualitatively impacts the DSF's shape for a carbon-contaminated deuterium and tritium plasma under NIF hot-spot conditions. In the Appendixes, we provide numerical implementations of the completed Mermin susceptibility, for the reader's convenience. Further, we produce a non-Drude conductivity model, by taking the single-species limit and introducing free parameters in the terms that enforce number and momentum conservation. To illustrate how number and momentum conservation impact the dynamical conductivity shape, we apply our conductivity model to dynamical gold conductivity measurements [Chen et al., Nature Commun. 12, 1638 (2021)]. Finally, comparing our model to the Drude-Smith conductivity model, we conclude that Smith's phenomenological parameter violates local number conservation.

A free energy lattice Boltzmann model has been developed to describe a binary system consisting of a nonideal solvent and a gaseous ideal solute. A free energy functional to describe this mixture has been derived, and it is used to determine the driving forces for two lattice Boltzmann equations, one for each component. The well-balanced lattice Boltzmann method is used to avoid discretization errors, which allows correct thermodynamic equilibrium to be achieved for both components as well as high density ratios. In this model, the distribution of the solute between the liquid and vapor phases of the solvent follows Henry's law due to the contributions of the two components to the free energy density. The momenta of the two components are coupled through the use of a mixture velocity in the equilibrium distributions of both components. The model also includes surface tension due to gradients of the solvent density and diffusion due to an added mobility term. The effects of model parameters on phase composition, surface tension, and the rate of solute transport are characterized, with examples of static gas bubbles and flat interfaces demonstrated. Mass transfer of the soluble component in the liquid phase of the nonideal component is characterized, and an equation for the solute diffusion coefficient is provided.

We show with molecular dynamics simulations that spinodal decomposition is a probable initiation mechanism of spallation in impact-melted samples at extremely high strain rates. The formation of voids or bubbles is a secondary process following the spinodal amplification of density fluctuations. As a result, the spallation strength can be related to the inherent thermodynamic property of the liquid, i.e., the liquid-gas spinodal curve, which can be determined by independent equation-of-state studies in prior. This connection between high strain-rate spallation and spinodal decomposition may be further examined in future experiments.

This Letter introduces a generalization of known duplication-divergence models for growing random graphs. This general duplication-divergence model includes a coupled divergence asymmetry rate, which allows to obtain the structure of random growing networks by duplication divergence in a continuous range of configurations between two known limit cases: (i) complete asymmetric divergence, i.e., the divergence rates affect only the edges of either the original or the copy vertex, and (ii) symmetric divergence, i.e., the divergence rates affect with equal probability both the original and the copy vertex. Connected components emerge as the divergence asymmetry rate slightly moves from the complete asymmetric divergence case. Mean-field results of prior published models are nicely reproduced by this generalization. In special cases, the connected component size distribution $C_s$ suggests a power-law scaling of the form $C_s\sim s^{-\lambda }$ for $s>1$, e.g., with $\lambda \approx 5/3$ for a divergence rate $\delta \approx 0.7$.

In this work, we investigate a system of three entangled qubits within the XXX model, subjected to an external magnetic field in the $z$ direction and incorporating an anisotropy term along the $y$ axis. We explore the system's thermodynamics by calculating its magnetic susceptibility and analyzing how this quantity encodes information about entanglement. By deriving rigorous bounds for the susceptibility, we demonstrate that violations of these bounds serve as an entanglement witness. Our results show that anisotropy enhances entanglement, extending the temperature range over which it persists. Furthermore, when the system is traced over the degrees of freedom of two qubits, the reduced entropy of the remaining single qubit corresponds to that of a system in a thermal bath with temperature $T>0\mathrm{K}$.

We present a simple model of a crucial phenomenon in modern societies: The shift from local to centralized production, leading to economies of scale and mass production transported over long-distance networks. Agents combine two distinct (and limited) resources, time and raw materials, either to produce for self-consumption or to sell on the market. The model shows a rich landscape of diverse production regimes, including mixed regimes where agents optimize utility by combining time spent working for the market, for self-subsistence, or by taking time off.

Lightning is a source of x-ray and gamma radiation, one of the most powerful natural photon emissions on Earth. In the paper, based on recently published measurement data, we explain the experimental results and state that the observed high-energy radiation is generated by synchrotron and cyclotron radiation mechanisms. The existence of fast electromagnetic surface plasmon waves propagating along the lightning discharge channel at a speed close to the speed of light in a vacuum is shown. A physical model of the formation of a vortex current in a plasma channel of lightning discharges due to the anomalous Hall effect caused by the phenomenon of relativistic spin-orbit interaction is proposed. The spin properties of electrons become important at relativistic velocities, so the spin-orbit coupling manifests itself as an effective magnetic force acting on the electron's spin, leading to the formation of a vortex current in the absence of an external magnetic field. This allows us to consider the lightning discharge channel as a charged particle accelerator that generates microwave, x-ray, gamma, and radio frequency radiation with a current pulse moving along a spiral trajectory by synchrotron and cyclotron radiation mechanisms. The proposed theoretical model of the formation of plasmon-enhanced emission of high-energy photons is consistent with observations of lightning and spark discharges in the atmosphere.