Physical Review E最新文献

Coupled oscillator models are of fundamental importance for understanding the collective dynamics that underlie many realistic applications ranging from physics and biology to human society. Here, we investigate the dynamics of oscillation quenching in a system of globally coupled Stuart-Landau limit-cycle oscillators incorporating the random heterogeneous interactions. We aim to provide a generic approach to systematically comprehending stability properties, as well as to appreciating the underlying emergent mechanism, of the quenching dynamics under the impression of inhomogeneous couplings. Importantly, we uncover that the peculiar symmetry of the linearized system profoundly facilitates the analysis of the algebraic structures of the eigenspectrum, thereby reformulating the characteristic equations deciding the eigenvalues in the simple forms for both finite and infinite sizes of the coupled system. In particular, the critical conditions manifesting the onset of oscillation quenching can be analytically characterized in terms of the matrix theory with finite-rank perturbation. Our work, thus, is capable of providing insights for controlling and regulating the oscillatory dynamics in complex systems consisting of interacting agents with large degrees of freedom.

The problem of estimating entropy production from incomplete information in stochastic thermodynamics is essential for theory and experiments. Whereas a considerable amount of work has been done on this topic, arguably, most of it is restricted to the case of nonequilibrium steady states driven by a fixed thermodynamic force. Based on a recent method that has been proposed for nonequilibrium steady states, we obtain an estimate of the entropy production based on the statistics of visible transitions and their waiting times for the case of periodically driven systems. The time dependence of transition rates in periodically driven systems produces several differences in relation to steady states, which is reflected in the entropy production estimation. More specifically, we propose an estimate that does depend on the time between transitions but is independent of the specific time of the first transition, thus it does not require tracking the protocol. Formally, this elimination of the timedependence of the first transition leads to an extra term in the inequality that involves the rate of entropy production and its estimate. We analyze a simple model of a molecular pump to understand the relation between the performance of the method and physical quantities such as energies, energy barriers, and thermodynamic affinity. Our results with this model indicate that the emergence of net motion in the form of a probability current in the space of states is a necessary condition for a relevant estimate of the rate of entropy production.

Fibrin polymerization is responsible for the formation of blood clots and is used in many biomedical applications. Considering polymerization as a dynamic phase transition, we constructed a scaling theory of fibrin networks formation. We show that in the transient state, protofibrils and branched clusters are self-assembled as a result of diffusion-controlled reactions with free fibrin monomers. The rate of reactions increases with initial concentrations of fibrinogen and thrombin. Protofibrils and clusters aggregate laterally, forming fibers, the elongation of which leads to their crosslinking to form a fibrin network. We calculated the network structure for different ratios of lag time and fibrinogen activation time. At a low ratio of fibrinogen and thrombin concentrations, sparse networks of thick and long fibers are formed, whereas at a high ratio, dense networks of thin and short fibers. The predicted concentration dependences of network parameters are in agreement with experimental data.

Propagation of ultrarelativistically intense laser pulses in a self-trapping mode in a near critical density plasma makes it possible to produce electron bunches of extreme parameters appropriate for different state of the art applications. Based on three-dimensional particle-in-cell (PIC) simulations, it has been demonstrated how the best efficiency of electron acceleration in terms of the total charge of high-energy electrons and laser-to-electron conversion rate can be achieved. For a given laser pulse energy the universal way is a proper matching of laser hot spot size and electron plasma density to the laser pulse duration. The recommendation to achieve the highest yield of high-energy electrons is to compress the laser pulse as much as possible. As an example, compression of a pulse of a few tens of femtoseconds to the ∼10 fs pulse leads to generation of the high-energy electron bunch with the highest total charge to exhibit conversion efficiency exceeding 50% for the Joule-level laser pulse energies.

We present a Brownian dynamics simulation of the bacterial Stirling engine studied by Krishnamurthy et al. [Nat. Phys. 12, 1134 (2016)1745-247310.1038/nphys3870]. In their experimental setup, an overdamped colloid in an optical trap with time-modulated stiffness interacts with a bacterial bath that we represent by an ensemble of overdamped active particles. In the parameter regime of the experiment the thermodynamic performance is governed by an effective temperature and can be parametrized analytically by active Brownian particle models. We quantitatively reproduce the efficiencies reported for the experiments under the assumption that energy exchange with the bath during isochores of the cycle is entirely recuperated and in agreement with the second law.

Multifractality of quantum states plays an important role for understanding numerous complex phenomena observed in different branches of physics. The multifractal properties of the eigenstates allow for characterising various phase transitions. In this work, we perform a thorough analysis of the impacts of an excited-state quantum phase transition (ESQPT) on the fractal behavior of both static and dynamical wave functions in a ferromagentic spin-1 Bose-Einstein condensate. By studying the features of the fractal dimensions, we show how the multifractality of eigenstates and time evolved states are affected by the presence of ESQPT. Specifically, the underlying ESQPT leads to a strong localization effect, which in turn enables us to use it as an indicator of ESQPT. We verify the ability of the fractal dimensions to probe the occurrence of ESQPT through a detailed scaling analysis. We also discuss how the ESQPT manifests itself in the fractal dimensions of the long-time averaged state. Our findings further confirm that the multifractal analysis is a powerful tool for studying of phase transitions in quantum many-body systems and also hint an potential application of ESQPTs in the burgeoning field of state preparation engineering.

We investigate the competing effects of the simultaneous presence of chirality and generalized tumbles in the dynamics of an active Brownian particle. Chiral active particles perform circular motions that give rise to slow transport at late times. By interrupting these circular trajectories at the right time by performing a tumble at the correct angle, we show that particles can enhance their diffusion. After deriving exact expressions for the orientational propagator and correlations, we use this to calculate the first two moments of displacement. For the effective diffusion coefficient, we study various optimal tumbling strategies. We show that under optimization of the tumbling rate, the case of symmetrically distributed tumbles always gives rise to enhanced diffusion, with an effective diffusion coefficient taking a universal value. Next, two cases are considered in detail, namely, directional reversal and tumbles at an arbitrary but fixed angle. We discuss how asymmetric tumbles can enhance diffusion beyond that of symmetric tumbles. Finally, we discuss a situation where the reorientations are realized dynamically in finite time.

We revisit the problem of describing creep in heterogeneous materials by an effective temperature by considering more realistic (and complex) non-mean-field elastic redistribution kernels. We show first, from theoretical considerations, that, if elastic stress redistribution and memory effects are neglected, the average creep failure time follows an Arrhenius expression with an effective temperature explicitly increasing with the quenched heterogeneity. Using a thermally activated progressive damage model of compressive failure, we show that this holds true when taking into account elastic interactions and memory effects, however, with an effective temperature T_{eff} depending as well on the nature of the (nondemocratic) elastic interaction kernel. We observe that the variability of creep lifetimes, for given external conditions of load and temperature, is roughly proportional to the mean lifetime and therefore depends as well on T, on quenched heterogeneity, and the elastic kernel. Finally, we discuss the implications of this effective temperature effect on the interpretation of macroscopic creep tests to estimate an activation volume at the microscale.

We perform a principal component analysis (PCA) of two one-dimensional lattice models belonging to distinct nonequilibrium universality classes-directed bond percolation and branching and annihilating random walks with an even number of offspring. We find that the uncentered PCA of data sets storing various system's configurations can be successfully used to determine the critical properties of these nonequilibrium phase transitions. In particular, in both cases, we obtain good estimates of the critical point and the dynamical critical exponent of the models. For directed bond percolation, we are furthermore able to extract critical exponents associated with the correlation length and the order parameter. We discuss the relation of our analysis with low-rank approximations of data sets.

We consider evolutionary games in which the agent selected for update compares strategies with q neighbors, rather than a single neighbor as in standard evolutionary game theory. If all q sampled neighbors agree, then agents update their strategy using a smoothed best-response rule. Following ideas from social impact theory, we also study mathematical generalizations of the dynamics to noninteger q>0. Looking at fixed point stability and fixation times for 2×2 games with all-to-all interactions, we find that the flow changes significantly as a function of q. Further, we develop the pair approximation for the q-deformed dynamics on uncorrelated graphs. We also study games with more than two strategies, such as the rock-paper-scissors game where we show that changing q leads to the emergence of new types of flow within the simplex.