9,983 research outputs found
Novel Phases and Finite-Size Scaling in Two-Species Asymmetric Diffusive Processes
We study a stochastic lattice gas of particles undergoing asymmetric
diffusion in two dimensions. Transitions between a low-density uniform phase
and high-density non-uniform phases characterized by localized or extended
structure are found. We develop a mean-field theory which relates
coarse-grained parameters to microscopic ones. Detailed predictions for
finite-size () scaling and density profiles agree excellently with
simulations. Unusual large- behavior of the transition point parallel to
that of self-organized sandpile models is found.Comment: 7 pages, plus 6 figures uuencoded, compressed and appended after
source code, LATeX, to be published as a Phys. Rev. Let
Comment on ``Dynamic behavior of anisotropic non-equilibrium driving lattice gases''
In a recent Letter Albano and Saracco study the dynamic critical behavior of
some anisotropic driven lattice gases by Monte Carlo (MC) simulations. In this
Comment we point out that the Ans\"atze they use to relate the measured scaling
exponents with the critical exponents analytically computed within different
field-theoretical approaches do not take properly into account the strongly
anisotropic nature of the phase transition, by implicitly assuming
. As a consequence, at variance with the claims
by the authors, their MC data are not conclusive to determine which one of the
field theories proposed in the literature correctly describes the universal
properties of the phase transition in these lattice gases.Comment: 1 pag
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Learning in a Small/Big World
This paper looks into how learning behavior changes with the complexity of the inference problem and the individual's cognitive ability, as I compare the optimal learning behavior with bounded memory in small and big worlds. A learning problem is a smal
Spiral cracks in drying precipitates
We investigate the formation of spiral crack patterns during the desiccation
of thin layers of precipitates in contact with a substrate. This
symmetry-breaking fracturing mode is found to arise naturally not from torsion
forces, but from a propagating stress front induced by the fold-up of the
fragments. We model their formation mechanism using a coarse-grain model for
fragmentation and successfully reproduce the spiral cracks. Fittings of
experimental and simulation data show that the spirals are logarithmic,
corresponding to constant deviation from a circular crack path. Theoretical
aspects of the logarithmic spirals are discussed. In particular we show that
this occurs generally when the crack speed is proportional to the propagating
speed of stress front.Comment: 4 pages, 5 figures, RevTe
Viability of competing field theories for the driven lattice gas
It has recently been suggested that the driven lattice gas should be
described by a novel field theory in the limit of infinite drive. We review the
original and the new field theory, invoking several well-documented key
features of the microscopics. Since the new field theory fails to reproduce
these characteristics, we argue that it cannot serve as a viable description of
the driven lattice gas. Recent results, for the critical exponents associated
with this theory, are re-analyzed and shown to be incorrect.Comment: 4 pages, revtex, no figure
Dynamic behavior of anisotropic non-equilibrium driving lattice gases
It is shown that intrinsically anisotropic non-equilibrium systems relaxing
by a dynamic process exhibit universal critical behavior during their evolution
toward non-equilibrium stationary states. An anisotropic scaling anzats for the
dynamics is proposed and tested numerically. Relevant critical exponents can be
evaluated self-consistently using both the short- and long-time dynamics
frameworks. The obtained results allow us to clarify a long-standing
controversy about the theoretical description, the universality and the origin
of the anisotropy of driven diffusive systems, showing that the standard field
theory does not hold and supporting a recently proposed alternative theory.Comment: 4 pages, 2 figure
Is the particle current a relevant feature in driven lattice gases?
By performing extensive MonteCarlo simulations we show that the infinitely
fast driven lattice gas (IDLG) shares its critical properties with the randomly
driven lattice gas (RDLG).
All the measured exponents, scaling functions and amplitudes are the same in
both cases. This strongly supports the idea that the main relevant
non-equilibrium effect in driven lattice gases is the anisotropy (present in
both IDLG and RDLG) and not the particle current (present only in the IDLG).
This result, at odds with the predictions from the standard theory for the
IDLG, supports a recently proposed alternative theory. The case of finite
driving fields is also briefly discussed.Comment: 4 pages. Slightly improved version. Journal Reference: To appear in
Phys. Rev. Let
Heuristic derivation of continuum kinetic equations from microscopic dynamics
We present an approximate and heuristic scheme for the derivation of
continuum kinetic equations from microscopic dynamics for stochastic,
interacting systems. The method consists of a mean-field type, decoupled
approximation of the master equation followed by the `naive' continuum limit.
The Ising model and driven diffusive systems are used as illustrations. The
equations derived are in agreement with other approaches, and consequences of
the microscopic dependences of coarse-grained parameters compare favorably with
exact or high-temperature expansions. The method is valuable when more
systematic and rigorous approaches fail, and when microscopic inputs in the
continuum theory are desirable.Comment: 7 pages, RevTeX, two-column, 4 PS figures include
The Radon Monitoring System in Daya Bay Reactor Neutrino Experiment
We developed a highly sensitive, reliable and portable automatic system
(H) to monitor the radon concentration of the underground experimental
halls of the Daya Bay Reactor Neutrino Experiment. H is able to measure
radon concentration with a statistical error less than 10\% in a 1-hour
measurement of dehumidified air (R.H. 5\% at 25C) with radon
concentration as low as 50 Bq/m. This is achieved by using a large radon
progeny collection chamber, semiconductor -particle detector with high
energy resolution, improved electronics and software. The integrated radon
monitoring system is highly customizable to operate in different run modes at
scheduled times and can be controlled remotely to sample radon in ambient air
or in water from the water pools where the antineutrino detectors are being
housed. The radon monitoring system has been running in the three experimental
halls of the Daya Bay Reactor Neutrino Experiment since November 2013
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Characterization of silicon nanowire by use of full-vectorial finite element method.
We have carried out a rigorous H-field-based full-vectorial modal analysis and used it to characterize, more accurately, the abrupt dielectric discontinuity of a high index contrast optical waveguide. The full-vectorial H and E fields and the Poynting vector profiles are described in detail. It has been shown through this work that the mode profile of a circular silicon nanowire is not circular and also contains a strong axial field component. The single-mode operation, vector field profiles, modal hybridness, modal ellipticity, and group velocity dispersion of this silicon nanowire are also presented
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