arXiv subjects

J. Luczka

Publications and source records attributed to J. Luczka.

24 records · Page 2Linked to original sources

arXiv2005

Quantum diffusion in biased washboard potentials: strong friction limit

Diffusive transport properties of a quantum Brownian particle moving in a tilted spatially periodic potential and strongly interacting with a thermostat are explored. Apart from the average stationary velocity, we foremost investigate the diffusive behavior by evaluating the effective diffusion coefficient together with the corresponding Peclet number. Corrections due to quantum effects, such as quantum tunneling and quantum fluctuations, are shown to substantially enhance the effectiveness of diffusive transport if only the thermostat temperature resides within an appropriate interval of intermediate values.

cond-mat.stat-mech↗

arXiv2004

On temperature- and space-dimension dependent matter agglomeration in a mature growing stage

Model matter agglomerations, with temperature as leading control parameter, have been considered, and some of their characteristics have been studied. The primary interest has been focused on the grain volume fluctuations, the magnitude of which readily differentiates between two commonly encountered types of matter agglomeration/aggregation processes, observed roughly for high- and low-density matter organizations. The two distinguished types of matter arrangements have been described through the (entropic) potential driving system. The impact of the potential type on the character of matter agglomeration has been studied, preferentially for (low density) matter agglomeration for which a logarithmic measure of its speed has been proposed. A common diffusion as well as mechanical relaxation picture, emerging during the mature growing stage, has been drawn using a phenomenological line of argumentation. Applications, mostly towards obtaining soft agglomerates of so-called jammed materials, have been mentioned.

cond-mat.soft↗

arXiv2004

Brownian motors: current fluctuations and rectification efficiency

With this work we investigate an often neglected aspect of Brownian motor transport: The rôle of fluctuations of the noise-induced current and its consequences for the efficiency of rectifying noise. In doing so, we consider a Brownian inertial motor that is driven by an unbiased monochromatic, time-periodic force and thermal noise. Typically, we find that the asymptotic, time- and noise-averaged transport velocities are small, possessing rather broad velocity fluctuations. This implies a corresponding poor performance for the rectification power. However, for tailored profiles of the ratchet potential and appropriate drive parameters, we can identify a drastic enhancement of the rectification efficiency. This regime is marked by persistent, uni-directional motion of the Brownian motor with few back-turns, only. The corresponding asymmetric velocity distribution is then rather narrow, with a support that predominantly favors only one sign for the velocity.

cond-mat.stat-mech↗

arXiv2004

Brownian motion: a case of temperature fluctuations

A diffusion process of a Brownian particle in a medium of temperature $T$ is re-considered. We assume that temperature of the medium fluctuates around its mean value. The velocity probability distribution is obtained. It is shown that the stationary state is not a thermodynamic equilibrium state described by the Maxwell distribution. Instead a nonequilibrium state is produced by temperature fluctuations.

cond-mat.stat-mech↗

arXiv2002

Currents in Systems of Mesoscopic Noisy Rings

A semi-phenomenological model is proposed to study dynamics and stedy states of magnetic fluxes and currents in mesoscopic rings and cylinders at non-zero temperature. The model is based on a Langevin equation for flux subject to zero-mean thermal equilibrium Nyquist noise. Quenched randomness, which mimics disorder, is included via the fluctuating parameter method. In the noiseless case, the stability threshold (critical temperature) exists below which selfsustaining currents can run even if the external flux is switched off. It is shown that selfsustaining and persistent currents survive in presence of Nyquist noise and quenched disorder but the stability threshold can be shifted by noise.

cond-mat↗

arXiv2002

Nonequilibrium coupled Brownian phase oscillators

A model of globally coupled phase oscillators under equilibrium (driven by Gaussian white noise) and nonequilibrium (driven by symmetric dichotomic fluctuations) is studied. For the equilibrium system, the mean-field state equation takes a simple form and the stability of its solution is examined in the full space of order parameters. For the nonequilbrium system, various asymptotic regimes are obtained in a closed analytical form. In a general case, the corresponding master equations are solved numerically. Moreover, the Monte-Carlo simulations of the coupled set of Langevin equations of motion is performed. The phase diagram of the nonequilibrium system is presented. For the long time limit, we have found four regimes. Three of them can be obtained from the mean-field theory. One of them, the oscillating regime, cannot be predicted by the mean-field method and has been detected in the Monte-Carlo numerical experiments.

cond-mat.stat-mech↗