7,871 research outputs found
Wavelet transforms in a critical interface model for Barkhausen noise
We discuss the application of wavelet transforms to a critical interface
model, which is known to provide a good description of Barkhausen noise in soft
ferromagnets. The two-dimensional version of the model (one-dimensional
interface) is considered, mainly in the adiabatic limit of very slow driving.
On length scales shorter than a crossover length (which grows with the strength
of surface tension), the effective interface roughness exponent is
, close to the expected value for the universality class of the
quenched Edwards-Wilkinson model. We find that the waiting times between
avalanches are fully uncorrelated, as the wavelet transform of their
autocorrelations scales as white noise. Similarly, detrended size-size
correlations give a white-noise wavelet transform. Consideration of finite
driving rates, still deep within the intermittent regime, shows the wavelet
transform of correlations scaling as for intermediate frequencies.
This behavior is ascribed to intra-avalanche correlations.Comment: RevTeX, 10 pages, 9 .eps figures; Physical Review E, to be publishe
Destruction of Anderson localization by a weak nonlinearity
We study numerically a spreading of an initially localized wave packet in a
one-dimensional discrete nonlinear Schr\"odinger lattice with disorder. We
demonstrate that above a certain critical strength of nonlinearity the Anderson
localization is destroyed and an unlimited subdiffusive spreading of the field
along the lattice occurs. The second moment grows with time , with the exponent being in the range . For small
nonlinearities the distribution remains localized in a way similar to the
linear case.Comment: 4 pages, 5 fig
Massive Black Hole Binary Systems in Hierarchical Scenario of Structure Formation
The hierarchical scenario of structure formation describes how objects like
galaxies and galaxy clusters are formed by mergers of small objects. In this
scenario, mergers of galaxies can lead to the formation of massive black hole
(MBH) binary systems. On the other hand, the merger of two MBH could produce a
gravitational wave signal detectable, in principle, by the Laser Interferometer
Space Antenna (LISA). In the present work, we use the Press-Schechter
formalism, and its extension, to describe the merger rate of haloes which
contain massive black holes. Here, we do not study the gravitational wave
emission of these systems. However, we present an initial study to determine
the number of systems formed via mergers that could permit, in a future
extension of this work, the calculation of the signature in gravitational waves
of these systems.Comment: to match the published version in International Journal of Modern
Physics
Optimal Cosmic-Ray Detection for Nondestructive Read Ramps
Cosmic rays are a known problem in astronomy, causing both loss of data and
data inaccuracy. The problem becomes even more extreme when considering data
from a high-radiation environment, such as in orbit around Earth or outside the
Earth's magnetic field altogether, unprotected, as will be the case for the
James Webb Space Telescope (JWST). For JWST, all the instruments employ
nondestructive readout schemes. The most common of these will be "up the ramp"
sampling, where the detector is read out regularly during the ramp. We study
three methods to correct for cosmic rays in these ramps: a two-point difference
method, a deviation from the fit method, and a y-intercept method. We apply
these methods to simulated nondestructive read ramps with single-sample groups
and varying combinations of flux, number of samples, number of cosmic rays,
cosmic-ray location in the exposure, and cosmic-ray strength. We show that the
y-intercept method is the optimal detection method in the read-noise-dominated
regime, while both the y-intercept method and the two-point difference method
are best in the photon-noise-dominated regime, with the latter requiring fewer
computations.Comment: To be published in PASP. This paper is 12 pages long and includes 15
figure
A Model for the Propagation of Sound in Granular Materials
This paper presents a simple ball-and-spring model for the propagation of
small amplitude vibrations in a granular material. In this model, the
positional disorder in the sample is ignored and the particles are placed on
the vertices of a square lattice. The inter-particle forces are modeled as
linear springs, with the only disorder in the system coming from a random
distribution of spring constants. Despite its apparent simplicity, this model
is able to reproduce the complex frequency response seen in measurements of
sound propagation in a granular system. In order to understand this behavior,
the role of the resonance modes of the system is investigated. Finally, this
simple model is generalized to include relaxation behavior in the force network
-- a behavior which is also seen in real granular materials. This model gives
quantitative agreement with experimental observations of relaxation.Comment: 21 pages, requires Harvard macros (9/91), 12 postscript figures not
included, HLRZ preprint 6/93, (replacement has proper references included
Simulation of neutrino and charged particle production and propagation in the atmosphere
A precise evaluation of the secondary particle production and propagation in
the atmosphere is very important for the atmospheric neutrino oscillation
studies. The issue is addressed with the extension of a previously developed
full 3-Dimensional Monte-Carlo simulation of particle generation and transport
in the atmosphere, to compute the flux of secondary protons, muons and
neutrinos. Recent balloon borne experiments have performed a set of accurate
flux measurements for different particle species at different altitudes in the
atmosphere, which can be used to test the calculations for the atmospheric
neutrino production, and constrain the underlying hadronic models. The
simulation results are reported and compared with the latest flux measurements.
It is shown that the level of precision reached by these experiments could be
used to constrain the nuclear models used in the simulation. The implication of
these results for the atmospheric neutrino flux calculation are discussed.Comment: 11 pages, 9 figure
New set of measures to analyze non-equilibrium structures
We introduce a set of statistical measures that can be used to quantify
non-equilibrium surface growth. They are used to deduce new information about
spatiotemporal dynamics of model systems for spinodal decomposition and surface
deposition. Patterns growth in the Cahn-Hilliard Equation (used to model
spinodal decomposition) are shown to exhibit three distinct stages. Two models
of surface growth, namely the continuous Kardar-Parisi-Zhang (KPZ) model and
the discrete Restricted-Solid-On-Solid (RSOS) model are shown to have different
saturation exponents
Women of "The Wire"
In this paper we analyze the representation of women on the popular television show The Wire. We discuss how, while writers attempt to portray race, crime, and inner-city life with sociological accuracy, characterizations of women, and of violence against women, are not especially complex or realistic. In particular, the crime of rape is underrepresented. While the show does feature certain competent, successful professional women, overall the portrayal of underclass women differs significantly from that of underclass men, featuring far fewer sympathetic female characters and demonizing several. In these ways the show succumbs to the sexist, patriarchal norms that characterize much of the representation of women in popular entertainment products. Some posit that this asymmetry of gender representation results from the male-oriented street experience of the show's male writers.En aquest treball s'analitza la representació de la dona en el popular programa de televisió The Wire (El cable). Discutim com, mentre que els escriptors intenten retratar la raça, el crim i la vida a les ciutats amb precisió sociològica, les caracteritzacions de la dona i de la violència contra la dona no són especialment complexes o realistes. En particular, el delicte de violació està infrarepresentat. Encara que l'espectacle presenta diverses dones competents i amb èxit professional, en general, el retrat de les dones de classe baixa difereix significativament del dels homes de classe baixa. Així, presenta els personatges femenins molt menys solidaris i fins i tot en demonitza uns quants. El programa sucumbeix, doncs, a les normes sexistes i patriarcals que caracteritzen gran part de les representacions de la dona en productes d'entreteniment popular. Alguns postulen que aquesta asimetria de la representació de gènere és el resultat de l'experiència del carrer fonamentalment androcèntrica dels escriptors del programa.En este trabajo se analiza la representación de la mujer en el popular programa de televisión The Wire (El cable). Discutimos cómo, mientras que los escritores intentan retratar la raza, el crimen y la vida en las ciudades con precisión sociológica, las caracterizaciones de la mujer y de la violencia contra la mujer no son especialmente complejas o realistas. En particular, el delito de violación está infrarrepresentado. Aunque el espectáculo presenta a varias mujeres competentes y con éxito profesional, en general, el retrato de las mujeres de clase baja difiere significativamente del de los hombres de clase baja. Así, presenta a los personajes femeninos mucho menos solidarios e incluso demoniza a varios. El programa sucumbe, pues, a las normas sexistas y patriarcales que caracterizan gran parte de las representaciones de la mujer en productos de entretenimiento popular. Algunos postulan que esta asimetría de la representación de género es el resultado de la experiencia de la calle fundamentalmente androcéntrica de los escritores del programa
New Evidence of Discrete Scale Invariance in the Energy Dissipation of Three-Dimensional Turbulence: Correlation Approach and Direct Spectral Detection
We extend the analysis of [Zhou and Sornette, Physica D 165, 94-125, 2002]
showing statistically significant log-periodic corrections to scaling in the
moments of the energy dissipation rate in experiments at high Reynolds number
() of three-dimensional fully developed turbulence. First, we
develop a simple variant of the canonical averaging method using a rephasing
scheme between different samples based on pairwise correlations that confirms
Zhou and Sornette's previous results. The second analysis uses a simpler local
spectral approach and then performs averages over many local spectra. This
yields stronger evidence of the existence of underlying log-periodic
undulations, with the detection of more than 20 harmonics of a fundamental
logarithmic frequency corresponding to the preferred
scaling ratio .Comment: 9 RevTex4 papes including 8 eps figure
LISA Science Results in the Presence of Data Disturbances
Each spacecraft in the Laser Interferometer Space Antenna houses a proof mass
which follows a geodesic through spacetime. Disturbances which change the proof
mass position, momentum, and/or acceleration will appear in the LISA data
stream as additive quadratic functions. These data disturbances inhibit signal
extraction and must be removed. In this paper we discuss the identification and
fitting of monochromatic signals in the data set in the presence of data
disturbances. We also present a preliminary analysis of the extent of science
result limitations with respect to the frequency of data disturbances
- …