I report on experiments demonstrating the appearance of Wood's anomalies in surface gravity waves propagating along a channel with a submerged obstacle. Space-time measurements of surface gravity waves allow one to compute the stationary complex field of the wave and the amplitude growth of localized and propagative modes over all the entire channel, including the scattering region. This allows one to access the near and far field dynamics, which constitute a new and complementary way of observation of mode resonances of the incoming wave displaying Wood's anomalies. Transmission coefficient, dispersion relations and normalized wave energy of the incoming wave and the excited mode are measured and found to be in good agreement with theoretical predictions.

At molecular scales, fluctuations play a significant role and prevent biomolecular processes from always proceeding in a preferred direction, raising the question of how limited amounts of free energy can be dissipated to obtain directed progress. We examine the system and process characteristics that efficiently break time-reversal symmetry at fixed energy loss; in particular for a simple model of a molecular machine, an intermediate energy barrier produces unusually high asymmetry for a given dissipation. We relate the symmetry-breaking factors found in this model to recent observations of biomolecular machines.

We study the equivalence between the recently proposed finite environment quantum jump model and a master equation approach. We derive microscopically the master equation for a qubit coupled to a finite bosonic environment and show that the master equation is equivalent to the finite environment quantum jump model. We analytically show that both the methods produce the same moments of work when the work is defined through the two-measurement protocol excluding the interaction energy. However, when compared to the work moments computed using the power operator approach, we find a difference in the form of the work moments. To numerically verify our results, we study a qubit coupled to an environment consisting of ten two-level systems.

We study a quantum XX chain coupled to two heat reservoirs that act on multiple sites and are kept at different temperatures and chemical potentials. The baths are described by Lindblad dissipators, which are constructed by direct coupling to the fermionic normal modes of the chain. Using a perturbative method, we are able to find analytical formulas for all steady-state properties of the system. We compute both the particle or magnetization current and the energy current, both of which are found to have the structure of Landauer's formula. We also obtain exact formulas for the Onsager coefficients. All properties are found to differ substantially from those of a single-site bath. In particular, we find a strong dependence on the intensity of the bath couplings. In the weak-coupling regime, we show that the Onsager reciprocal relations are satisfied.

We study a generalization of the $XY$ model with an additional nematic-like term through extensive numerical simulations and finite-size techniques, both in two and three dimensions. While the original model favors local alignment, the extra term induces angles of $2\pi /q$ between neighboring spins. We focus here on the $q=8$ case (while presenting new results for other values of $q$ as well) whose phase diagram is much richer than the well-known $q=2$ case. In particular, the model presents not only continuous, standard transitions between Berezinskii-Kosterlitz-Thouless (BKT) phases as in $q=2$, but also infinite-order transitions involving intermediate, competition-driven phases absent for $q=2$ and 3. Besides presenting multiple transitions, our results show that having vortices decoupling at a transition is not a sufficient condition for it to be of BKT type.

We observe the hysteresis of a spontaneous symmetry breaking (SSB) transition in a parametrically modulated magneto-optical trap by sweeping the total number of atoms and study thermal hysteretic behavior in the system by measuring the scaling exponent of hysteresis. It is shown that the relaxation time of the order parameter in the SSB transition becomes larger near the critical number. The scaling exponent of the hysteresis area with number sweeping rate is found to be $0.64\pm 0.04$, which is consistent with the value in the mean-field model.

The present work follows our previous study dealing with a new type of synchronization in a system of two weakly coupled generalized van der Pol–Duffing autogenerators. The essence of the effect revealed is that the synchronized oscillations are not stationary but accompanied by the most intensive energy exchange between the oscillators. The phase shift between the generators remains constant most of the time, except for vanishingly small transitional intervals. The current analysis deals with a generalized model in order to clarify the frequency detuning effect. We found that varying the frequency detuning, nonlinearity, and dissipation parameters can lead to structural changes in phase diagrams of the energy exchange dynamics, with important transitions from the intensive energy exchange to its localization on one of the two oscillators. The main conclusion is that stationary and nonstationary synchronizations associate with nonlinear normal and local modes, respectively. The analysis uses phase plane diagrams, including the concept of limiting phase trajectories, whose role in nonstationary synchronization appears to be similar to the role of nonlinear normal modes in conventional stationary states.

We study the effect of an isotropic-nematic $(I-N)$ phase transition on the liquid crystal alignment at untreated polymer surfaces. We demonstrate that the pattern at the untreated substrate in the planar cell where the other substrate is uniformly rubbed strongly depends on the temperature gradient across the cell during the $I-N$ phase transition, being macroscopically isotropic if the untreated substrate is cooled faster, but becoming almost homogeneous along the rubbing direction in the opposite temperature gradient. We interpret the observed effect using complementary models of heat transfer and nematic elasticity. Based on the heat transfer model we show that the asymmetric temperature conditions in our experiments provide unidirectional propagation of the $I-N$ interface during the phase transition and determine the initial director orientation pattern at the test's untreated surface. Using the Frank-Oseen model of nematic elasticity, we represent the three-dimensional director field in the nematic cell as a two-dimensional (2D) pattern at the untreated surface and perform 2D numeric simulations. The simulations explain the experimental results: Different initial director orientations at the untreated surface evolve into different stationary patterns.

This study numerically and analytically investigates the dynamics of a rotor under viscous or dry friction as a nonequilibrium probe of a granular gas. In order to demonstrate the role of the rotor as a probe for a nonequilibrium bath, the molecular dynamics (MD) simulation of the rotor is performed under viscous or dry friction surrounded by a steady granular gas under gravity. A one-to-one map between the velocity distribution function (VDF) of the granular gas and the angular distribution function for the rotor is theoretically derived. The MD simulation demonstrates that the one-to-one map accurately infers the local VDF of the granular gas from the angular VDF of the rotor, and vice versa.

Similarities between force-driven compression experiments of porous materials and earthquakes have been recently proposed. In this paper, we measure the acoustic emission during displacement-driven compression of a porous glass. The energy of acoustic-emission events shows that the failure process exhibits avalanche scale-invariance and therefore follows the Gutenberg-Richter law. The resulting exponents do not exhibit significant differences with respect the force-driven case. Furthermore, the force exhibits an avalanche-type behavior for which the force drops are power-law distributed and correlated with the acoustic emission events.

Using recently obtained ac conductivity data we have derived dc conductivity together with free electron density and electron momentum relaxation time in two-temperature warm dense gold with energy density up to 4.1 MJ/kg ($0.8\times {10}^{11}\mathrm{J}/{\mathrm{m}}^3$). The derivation is based on a Drude interpretation of the dielectric function that takes into account contributions of intraband and interband transitions as well as atomic polarizability. The results provide valuable benchmarks for assessing the extended Ziman formula for electrical resistivity and an accompanying average atom model.

Symmetries constrain dynamics. We test this fundamental physical principle, experimentally and by molecular dynamics simulations, for a hot Janus swimmer operating far from thermal equilibrium. Our results establish scalar and vectorial steady-state fluctuation theorems and a thermodynamic uncertainty relation that link the fluctuating particle current to its entropy production at an effective temperature. A Markovian minimal model elucidates the underlying nonequilibrium physics.

We present the closed-loop approach to linear nonequilibrium thermodynamics considering a generic heat engine dissipatively connected to two temperature baths. The system is usually quite generally characterized by two parameters: the output power $P$ and the conversion efficiency $\eta$, to which we add a third one, the working frequency $\omega$. We establish that a detailed understanding of the effects of the dissipative coupling on the energy conversion process requires only knowing two quantities: the system's feedback factor $\beta$ and its open-loop gain $A_0$, which product $A_0\beta$ characterizes the interplay between the efficiency, the output power, and the operating rate of the system. By raising the abstract hermodynamic analysis to a higher level, the feedback loop approach provides a versatile and economical, hence fairly efficient, tool for the study of any conversion engine operation for which a feedback factor can be defined.

We investigate nonlinear localized magnetic excitations in a one-dimensional bicomponent magnonic crystal under a periodic magnetic field of spatially varying strength. The governing Landau-Lifshitz equation is transformed into a variable coefficient nonlinear Schrödinger (VCNLS) equation using stereographic projection. In general, the VCNLS equation is nonintegrable and by using Painlevé analysis, we obtain necessary conditions for the VCNLS equation to pass the Weiss-Tabor-Carnevale Painlevé test. A sufficient integrability condition is obtained by further exploring a transformation, which can map the VCNLS equation into the well-known standard nonlinear Schrödinger equation. The transformation builds a systematic connection between the solution of the standard nonlinear Schrödinger equation and VCNLS equation. The results show that the excitation of magnetization in the form of a soliton exists on the oscillatory background with a structure similar to the form of spin Bloch waves. Such a solution exists only when certain conditions on the coefficient of the VCNLS equation are satisfied. To corroborate the analytical results, we performed the numerical simulation by solving the governing VCNLS equation with integrability conditions using the split step Fourier method and the result agrees well with analytical results, and it suggests a way to control the dynamics of magnetization in the form of solitons by an appropriate spatial modulation of the nonlinearity coefficient in the governing VCNLS equation, which depends on the ferromagnetic materials which form the bicomponent magnonic crystal.

In times of plenty expectations rise, just as in times of crisis they fall. This can be mathematically described as a win-stay-lose-shift strategy with dynamic aspiration levels, where individuals aspire to be as wealthy as their average neighbor. Here we investigate this model in the realm of evolutionary social dilemmas on the square lattice and scale-free networks. By using the master equation and Monte Carlo simulations, we find that cooperators coexist with defectors in the whole phase diagram, even at high temptations to defect. We study the microscopic mechanism that is responsible for the striking persistence of cooperative behavior and find that cooperation spreads through second-order neighbors, rather than by means of network reciprocity that dominates in imitation-based models. For the square lattice the master equation can be solved analytically in the large temperature limit of the Fermi function, while for other cases the resulting differential equations must be solved numerically. Either way, we find good qualitative agreement with the Monte Carlo simulation results. Our analysis also reveals that the evolutionary outcomes are to a large degree independent of the network topology, including the number of neighbors that are considered for payoff determination on lattices, which further corroborates the local character of the microscopic dynamics. Unlike large-scale spatial patterns that typically emerge due to network reciprocity, here local checkerboard-like patterns remain virtually unaffected by differences in the macroscopic properties of the interaction network.

We study the dynamics of electric field driven multiaxis electro-orientation of birefringent microsheets in both the isotropic and nematic phases of a liquid crystal. For a fixed direction of applied field in the isotropic phase, there are two critical fields above which the microsheets show two orientations. In the nematic phase, it shows three rotations in both planar and homeotropic cells. These orientations are observed at varying voltages and wide time scales and are explained based on the competing effect of the electric, elastic, and viscous torques. The control of the orientation of anisotropic microparticles (both optically and geometrically) by transducing external energy may be useful in electro-optics and photonics.

The dynamics of the fluctuations of a liquid film on a heterogeneous substrate is analyzed. We consider the case of a viscous liquid in the Stokes limit, with small variations of substrate height and a small varying slip length. We discuss the possibility of extracting the topographic profile or the slip length profile at the liquid-solid interface from the measurement of the fluctuations of the free liquid surface. Our results, therefore, explore the theoretical basis of a strategy for a fluctuation-induced microscopy of immersed solids at the micrometer scale.

The question of how stiff polymers are able to pack into small containers is particularly relevant to the study of DNA packaging in viruses. A reduced version of the problem based on coarse-grained representations of the main components of the system—the DNA polymer and the spherical viral capsid—has been studied by molecular dynamics simulation. The results, involving longer polymers than in earlier work, show that as polymers become more rigid there is an increasing tendency to self-organize as spools that wrap from the inside out, rather than the inverse direction seen previously. In the final state, a substantial part of the polymer is packed into one or more coaxial spools, concentrically layered with different orientations, a form of packaging achievable without twisting the polymer.

In this paper we derive the non-Markovian barotropic-type and Hall-type fluctuation relations for noninteracting charged Brownian particles embedded in a memory heat bath and under the action of crossed electric and magnetic fields. We first obtain a more general non-Markovian fluctuation relation formulated within the context of a generalized Langevin equation with arbitrary friction memory kernel and under the action of a constant magnetic field and an arbitrary time-dependent electric field. It is shown that this fluctuation relation is related to the total amount of an effective work done on the charged particle as it is driven out of equilibrium by the applied time-dependent electric field. Both non-Markovian barotropic- and Hall-type fluctuation relations are then derived when the electric field is assumed to be also a constant vector pointing along just one axis. In the Markovian limit, we show explicitly that they reduce to the same results reported in the literature.

We investigate heat transport between two thermal reservoirs that are coupled via a large spin composed of $N$ identical two-level systems. One coupling implements the dissipative Dicke superradiance. The other coupling is locally of the pure-dephasing type and requires to go beyond the standard weak-coupling limit by employing a Bogoliubov mapping in the corresponding reservoir. After the mapping, the large spin is coupled to a collective mode with the original pure-dephasing interaction, but the collective mode is dissipatively coupled to the residual oscillators. Treating the large spin and the collective mode as the system, a standard master equation approach is now able to capture the energy transfer between the two reservoirs. Assuming fast relaxation of the collective mode, we derive a coarse-grained rate equation for the large spin only and discuss how the original Dicke superradiance is affected by the presence of the additional reservoir. Our main finding is a cooperatively enhanced rectification effect due to the interplay of supertransmittant heat currents (scaling quadratically with $N$) and the asymmetric coupling to both reservoirs. For large $N$, the system can thus significantly amplify current asymmetries under bias reversal, functioning as a heat diode. We also briefly discuss the case when the couplings of the collective spin are locally dissipative, showing that the heat-diode effect is still present.