10,617 research outputs found
Escape rate of an active Brownian particle over a potential barrier
We study the dynamics of an active Brownian particle with a nonlinear
friction function located in a spatial cubic potential. For strong but finite
damping, the escape rate of the particle over the spatial potential barrier
shows a nonmonotonic dependence on the noise intensity. We relate this behavior
to the fact that the active particle escapes from a limit cycle rather than
from a fixed point and that a certain amount of noise can stabilize the sojourn
of the particle on this limit cycle
Error distributions on large entangled states with non-Markovian dynamics
We investigate the distribution of errors on a computationally useful
entangled state generated via the repeated emission from an emitter undergoing
strongly non-Markovian evolution. For emitter-environment coupling of
pure-dephasing form, we show that the probability that a particular patten of
errors occurs has a bound of Markovian form, and thus accuracy threshold
theorems based on Markovian models should be just as effective. This is the
case, for example, for a charged quantum dot emitter in a moderate to strong
magnetic field. Beyond the pure-dephasing assumption, though complicated error
structures can arise, they can still be qualitatively bounded by a Markovian
error model.Comment: Close to published versio
Optimization of a neutrino factory oscillation experiment
We discuss the optimization of a neutrino factory experiment for neutrino
oscillation physics in terms of muon energy, baselines, and oscillation
channels (gold, silver, platinum). In addition, we study the impact and
requirements for detector technology improvements, and we compare the results
to beta beams. We find that the optimized neutrino factory has two baselines,
one at about 3000 to 5000km, the other at about 7500km (``magic'' baseline).
The threshold and energy resolution of the golden channel detector have the
most promising optimization potential. This, in turn, could be used to lower
the muon energy from about 50GeV to about 20GeV. Furthermore, the inclusion of
electron neutrino appearance with charge identification (platinum channel)
could help for large values of \sin^2 2 \theta_{13}. Though tau neutrino
appearance with charge identification (silver channel) helps, in principle, to
resolve degeneracies for intermediate \sin^2 2 \theta_{13}, we find that
alternative strategies may be more feasible in this parameter range. As far as
matter density uncertainties are concerned, we demonstrate that their impact
can be reduced by the combination of different baselines and channels. Finally,
in comparison to beta beams and other alternative technologies, we clearly can
establish a superior performance for a neutrino factory in the case \sin^2 2
\theta_{13} < 0.01.Comment: 51 pages, 25 figures, 6 tables, references corrected, final version
to appear in Phys. Rev.
A Paper at the ECE Symposium on Application of Economic-Mathematical Models in the Energy Sector, Alma-Ata September 1973
The energy sector of each country is a part of the national economic subsystems which directly and to a considerable degree has an influence on the growth rate of the national economy and the increase of national income. Therefore it is a permanent objective to always provide a rational basis for the provision of society with demand-determined supply of energy sources. A tool for the proper achievement of this goal is the application of mathematical-economic models for optimization of the energy sector with consideration of national economic constraints. It is in the interest of society to include the largest possible system in the optimization models. According to the current condition of our understanding, that type of objective can be achieved only with mathematical-economic system models which consider all essential economic, technological, technical, parameters, and to a limited degree also political-economic influences
Universal transport signatures of Majorana fermions in superconductor-Luttinger liquid junctions
One of the most promising proposals for engineering topological
superconductivity and Majorana fermions employs a spin-orbit coupled nanowire
subjected to a magnetic field and proximate to an s-wave superconductor. When
only part of the wire's length contacts to the superconductor, the remaining
conducting portion serves as a natural lead that can be used to probe these
Majorana modes via tunneling. The enhanced role of interactions in one
dimension dictates that this configuration should be viewed as a
superconductor-Luttinger liquid junction. We investigate such junctions between
both helical and spinful Luttinger liquids, and topological as well as
non-topological superconductors. We determine the phase diagram for each case
and show that universal low-energy transport in these systems is governed by
fixed points describing either perfect normal reflection or perfect Andreev
reflection. In addition to capturing (in some instances) the familiar
Majorana-mediated `zero-bias anomaly' in a new framework, we show that
interactions yield dramatic consequences in certain regimes. Indeed, we
establish that strong repulsion removes this conductance anomaly altogether
while strong attraction produces dynamically generated effective Majorana modes
even in a junction with a trivial superconductor. Interactions further lead to
striking signatures in the local density of states and the line-shape of the
conductance peak at finite voltage, and also are essential for establishing
smoking-gun transport signatures of Majorana fermions in spinful Luttinger
liquid junctions.Comment: 25 pages, 6 figures, v
Symmetric Brownian motor
In this paper we present a model of a symmetric Brownian motor (SBM) which
changes the sign of its velocity when the temperature gradient is inverted. The
velocity, external work and efficiency are studied as a function of the
temperatures of the baths and other relevant parameters. The motor shows a
current reversal when another parameter (a phase shift) is varied. Analytical
predictions and results from numerical simulations are performed and agree very
well. Generic properties of this type of motors are discussed.Comment: 8 pages and 10 figure
Effective phase description of noise-perturbed and noise-induced oscillations
An effective description of a general class of stochastic phase oscillators
is presented. For this, the effective phase velocity is defined either by
invariant probability density or via first passage times. While the first
approach exhibits correct frequency and distribution density, the second one
yields proper phase resetting curves. Their discrepancy is most pronounced for
noise-induced oscillations and is related to non-monotonicity of the phase
fluctuations
Monitoring spatially heterogeneous dynamics in a drying colloidal thin film
We report on a new type of experiment that enables us to monitor spatially
and temporally heterogeneous dynamic properties in complex fluids. Our approach
is based on the analysis of near-field speckles produced by light diffusely
reflected from the superficial volume of a strongly scattering medium. By
periodic modulation of an incident speckle beam we obtain pixel-wise ensemble
averages of the structure function coefficient, a measure of the dynamic
activity. To illustrate the application of our approach we follow the different
stages in the drying process of a colloidal thin film. We show that we can
access ensemble averaged dynamic properties on length scales as small as ten
micrometers over the full field of view.Comment: To appear in Soft Material
Recommendations for nomenclature of ionselective electrodes (IUPAC Recommendations 1994)
The rapid growth of interest in the field of ion-selective electrodes (ISEs), within the larger field of electrochemical sensors based on potentiometric, amperometric, and conductometric principles, makes it highly desirable to achieve improved standardization of nomenclature in this area. The previous document, WAC Recommendations 1975 (1) has been corrected using recent experimental and theoretical findings. This report does not define or recommend activity standards or calibration procedures using activity standard
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