2,954 research outputs found
Diffusion and Current of Brownian Particles in Tilted Piecewise Linear Potentials: Amplification and Coherence
Overdamped motion of Brownian particles in tilted piecewise linear periodic
potentials is considered. Explicit algebraic expressions for the diffusion
coefficient, current, and coherence level of Brownian transport are derived.
Their dependencies on temperature, tilting force, and the shape of the
potential are analyzed. The necessary and sufficient conditions for the
non-monotonic behavior of the diffusion coefficient as a function of
temperature are determined. The diffusion coefficient and coherence level are
found to be extremely sensitive to the asymmetry of the potential. It is
established that at the values of the external force, for which the enhancement
of diffusion is most rapid, the level of coherence has a wide plateau at low
temperatures with the value of the Peclet factor 2. An interpretation of the
amplification of diffusion in comparison with free thermal diffusion in terms
of probability distribution is proposed.Comment: To appear in PR
Noise-induced energy excitation by a general environment
We analyze the effects that general environments, namely ohmic and non-ohmic,
at zero and high temperature induce over a quantum Brownian particle. We state
that the evolution of the system can be summarized in terms of two main
environmental induced physical phenomena: decoherence and energy activation. In
this article we show that the latter is a post-decoherence phenomenon. As the
energy is an observable, the excitation process is a direct indication of the
system-environment entanglement particularly useful at zero temperature.Comment: 14 pages; 7 figures. Version to appear in Phys Lett.
Absolute negative mobility induced by white Poissonian noise
We research the transport properties of inertial Brownian particles which
move in a symmetric periodic potential and are subjected to both a symmetric,
unbiased time-periodic external force and biased Poissonian white shot noise
(of non-zero average F) being composed of a random sequence of delta-shaped
pulses with random amplitudes. Upon varying the parameters of white shot-noise
one conveniently can manipulate the transport direction and the overall
nonlinear response behavior. Within tailored parameter regimes, we find that
the response is opposite to the applied average bias F of such white shot
noise. This very transport characteristics thus mimics a nonlinear Absolute
Negative Mobility (ANM) regime. Moreover, such white shot noise driven ANM is
robust with respect to statistics of the shot noise spikes. Our findings can be
checked and corroborated experimentally by use of a setup that consists of a
single resistively and capacitively shunted Josephson junction device.Comment: 14 pages, 12 figures; accepted in J. Stat. Mech.: Theor. Exp. (2013
Fluctuation Spectra and Force Generation in Non-equilibrium Systems
Many biological systems are appropriately viewed as passive inclusions
immersed in an active bath: from proteins on active membranes to microscopic
swimmers confined by boundaries. The non-equilibrium forces exerted by the
active bath on the inclusions or boundaries often regulate function, and such
forces may also be exploited in artificial active materials. Nonetheless, the
general phenomenology of these active forces remains elusive. We show that the
fluctuation spectrum of the active medium, the partitioning of energy as a
function of wavenumber, controls the phenomenology of force generation. We find
that for a narrow, unimodal spectrum, the force exerted by a non-equilibrium
system on two embedded walls depends on the width and the position of the peak
in the fluctuation spectrum, and oscillates between repulsion and attraction as
a function of wall separation. We examine two apparently disparate examples:
the Maritime Casimir effect and recent simulations of active Brownian
particles. A key implication of our work is that important non-equilibrium
interactions are encoded within the fluctuation spectrum. In this sense the
noise becomes the signal
Driven Brownian transport through arrays of symmetric obstacles
We numerically investigate the transport of a suspended overdamped Brownian
particle which is driven through a two-dimensional rectangular array of
circular obstacles with finite radius. Two limiting cases are considered in
detail, namely, when the constant drive is parallel to the principal or the
diagonal array axes. This corresponds to studying the Brownian transport in
periodic channels with reflecting walls of different topologies. The mobility
and diffusivity of the transported particles in such channels are determined as
functions of the drive and the array geometric parameters. Prominent transport
features, like negative differential mobilities, excess diffusion peaks, and
unconventional asymptotic behaviors, are explained in terms of two distinct
lengths, the size of single obstacles (trapping length) and the lattice
constant of the array (local correlation length). Local correlation effects are
further analyzed by continuously rotating the drive between the two limiting
orientations.Comment: 10 pages 13 figure
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