Physical review. E最新文献

The motivation behind the proposed study stems from multilane traffic systems with finite availability of particles. Our investigation revolves around a totally asymmetric simple exclusion process incorporating a finite reservoir and the occurrence of lane-switching phenomena. The study delves into the system's characteristics, including phase diagrams, density profiles, phase transitions, finite-size effects, and shock positions. These analyses concern the number of particles within the system and various weak-coupling rates. The outcomes obtained from the generalized mean-field theory are cross-validated against the results derived from Monte Carlo simulations. In scrutinizing the system's dynamics, we observe several noteworthy observations. Notably, we identified critical mixed profiles featuring instances of double shocks. The system, intriguingly, demonstrates a transition known as reentrance transition. The study also reports a rare phenomenon, namely, the jumping effect within the shock profile, adding a layer of complexity to the system's behavior and proving the significance of limited resources.

We introduce the profligacy of a search process as a competition between its expected cost and the probability of finding the target. The arbiter of the competition is a parameter λ that represents how much a searcher invests into increasing the chance of success. Minimizing the profligacy with respect to the search strategy specifies the optimal search. We show that in the case of diffusion with stochastic resetting, the amount of resetting in the optimal strategy has a highly nontrivial dependence on model parameters resulting in classical continuous transitions, discontinuous transitions and tricritical points, as well as nonstandard discontinuous transitions exhibiting reentrant behavior and overhangs.

We study Ruelle-Pollicott resonances in translationally invariant quantum many-body lattice systems via spectra of a momentum-resolved operator propagator on infinite systems. Momentum dependence gives insight into the decay of correlation functions, showing that, depending on their symmetries, different correlation functions in general decay with different rates. Focusing on the kicked Ising model, the spectrum seems to be typically composed of an annular random matrix-like ring whose size we theoretically predict, and few isolated resonances. We identify several interesting regimes, including a mixing regime with a power-law decay of correlation functions. In that regime, we also observe a huge difference in timescales of different correlation functions due to an almost conserved operator. An exact expression for the singular values of the operator propagator is conjectured, showing that it becomes singular at a special point.

Granular fluids, as defined by a collection of moving solid particles, is a paradigm of a dissipative system out of equilibrium. Inelastic collisions between particles is the source of dissipation, and is the origin of a transition from a gas to a liquidlike state. This transition can be triggered by an increase of the solid fraction. Moreover, in compartmentalized systems, this condensation is driving the entire granular fluid into a Maxwell demon phenomenon, localizing most of the grains into a specific compartment. Classical approaches fail to capture these phenomena, thus motivating many experimental and numerical works. Herein, we demonstrate that the Onsager variational principle is able to predict accurately the coexistence of gas-liquid states in granular systems, opening ways to model other phenomena observed in such dissipative systems like segregation or the jamming transition.

Pair correlations for a polar liquid-crystal (LC) system have been theoretically investigated by means of integral equation approach. Using the dipolar Gay-Berne (GB) interactions between the molecules that composed the LC system, calculations of the nearest-neighbor (NN) and next-NN (NNN) correlators as well as the order parameters and the static dielectric coefficients were performed. It is shown that for a simple cubic packing, NN dipoles tend to be mutually antiparallel with respect to the central dipole, while the opposite trend was observed for NNN dipoles. Our calculations also show that the anisotropy of the nematic phase is not imposed by the symmetry of the system, but rather is a consequence of the dipolar GB potential.

Collisional Brownian engines have been proposed as alternatives to nonequilibrium nanoscale engines. However, most studies have focused on the simpler overdamped case, leaving the role of inertia much less explored. In this work, we introduce the idea of collisional engines to underdamped Brownian particles, where at each stage the particle is sequentially subjected to a distinct driving force. A careful comparison between the performance of underdamped and overdamped Brownian work-to-work engines has been undertaken. The results show that underdamped Brownian engines generally outperform their overdamped counterparts. A key difference is the presence of a resonant regime in underdamped engines, in which both efficiency and power output are enhanced across a broad set of parameters. Our study highlights the importance of carefully selecting dynamics and driving protocols to achieve optimal engine performance.

The transition from a ballistic to a diffusive regime of heat transfer is studied using two models. The first model is a one-dimensional chain with bonds, capable of dissociation. Interparticle forces in the chain are harmonic for bond deformations below a critical value, corresponding to the dissociation, and zero above this value. A kinetic description of heat transfer in the chain is proposed using the second model, namely, a gas of noninteracting quasiparticles, reflecting from randomly occurring barriers. The motion of quasiparticles mimicks heat (energy) transfer in the chain, while the barriers mimic dissociated bonds. For the gas, a kinetic equation is derived and solved analytically. The solution demonstrates the transition from the ballistic regime at small times to the diffusive regime at large times. In the diffusive limit, the distance traveled by a heat obeys square-root asymptotics as in the case of classical diffusion. However, the shape of the fundamental solution for temperature differs from the Gaussian function and therefore the Fourier law is not satisfied. Two examples are considered to demonstrate that the presented kinetic model is in good qualitative agreement with the results of the numerical solution of the chain dynamics. The presented results show that bond dissociation is an important mechanism underlying the transition from ballistic to diffusive heat transfer in one-dimensional chains.

Systems of oscillators subject to time-dependent noise typically achieve synchronization for long times when their mutual coupling is sufficiently strong. The dynamical process whereby synchronization is reached can be thought of as a growth process in which an interface formed by the local phase field gradually roughens and eventually saturates. Such a process is here shown to display the generic scale invariance of the one-dimensional Kardar-Parisi-Zhang universality class, including a Tracy-Widom probability distribution for phase fluctuations around their mean. This is revealed by numerical explorations of a variety of oscillator systems: rings of generic phase oscillators and rings of paradigmatic limit-cycle oscillators, like Stuart-Landau and van der Pol. It also agrees with analytical expectations derived under conditions of strong mutual coupling. The nonequilibrium critical behavior that we find is robust and transcends the details of the oscillators considered. Hence, it may well be accessible to experimental ensembles of oscillators in the presence of, e.g., thermal noise.

We study the effects of disorder on the exciton spectra in quantum well (QW) semiconductor structures. We model the disorder by introducing the fractional Laplacian into the Schrödinger equations, which describe the exciton spectra of the above QW structures. We calculate the exciton binding energies in its ground state and a few low-lying excited states as a function of the GaAs QW size. Our main finding is that disorder significantly increases the exciton binding energy in QWs, sometimes by a factor of 10. For disordered case, the interplay between strength of disorder (characterized by Lévy index α in our approach) and nonzero exciton angular momentum in its excited states causes the system to perceive QW finite physical barrier heights as infinite, which also influences the exciton binding energy. Our results can be applied for heterostructures like GaAs/AlGaAs, GaN/AlGaN, as well as to any of the II-VI and III-V heterostructures, which may be used in many optoelectronic and spintronic applications.

The out-of-equilibrium aggregation of dipolar particles, such as magnetized beads, leads to the formation of large structures composed of chains, loops, and eventually ribbons. In the present study, we focus on the evolution of these different substructures in a two-dimensional system confined within progressively shrinking environments. Using numerical simulations, we identify structural events as a function of the packing fraction. At low density, a percolation threshold ϕ_{p}≈0.15 is evidenced, where chainlike structures merge into a single large aggregate with significant voids. This gel-like structure then densifies as ϕ increases. At large ϕ values, crystallites of both square and hexagonal order phase appear, but they are far from extending over the whole system.