1,716 research outputs found
Quantum Turbulent Structure in Light
The infinite superpositions of random plane waves are known to be threaded
with vortex line singularities which form complicated tangles and obey strict
topological rules. We observe that within these structures a timelike axis
appears to emerge with which we can define vortex velocities in a useful way:
with both numerical simulations and optical experiments, we show that the
statistics of these velocities match those of turbulent quantum fluids such as
superfluid helium and atomic Bose-Einstein condensates. These statistics are
shown to be independent of system scale. These results raise deep questions
about the general nature of quantum chaos and the role of nonlinearity in the
structure of turbulence.Comment: 4 pages, 2 figure
Continuous Gravitational Waves from Isolated Galactic Neutron Stars in the Advanced Detector Era
We consider a simulated population of isolated Galactic neutron stars. The
rotational frequency of each neutron star evolves through a combination of
electromagnetic and gravitational wave emission. The magnetic field strength
dictates the dipolar emission, and the ellipticity (a measure of a neutron
star's deformation) dictates the gravitational wave emission. Through both
analytic and numerical means, we assess the detectability of the Galactic
neutron star population and bound the magnetic field strength and ellipticity
parameter space of Galactic neutron stars with or without a direct
gravitational wave detection. While our simulated population is primitive, this
work establishes a framework by which future efforts can be conducted.Comment: Accepted for publication by Physical Review D, 8 pages, 5 figure
Thomas-Fermi Approximation for a Condensate with Higher-order Interactions
We consider the ground state of a harmonically trapped Bose-Einstein
condensate within the Gross-Pitaevskii theory including the effective-range
corrections for a two-body zero-range potential. The resulting non-linear
Schr\"odinger equation is solved analytically in the Thomas-Fermi approximation
neglecting the kinetic energy term. We present results for the chemical
potential and the condensate profiles, discuss boundary conditions, and compare
to the usual Thomas-Fermi approach. We discuss several ways to increase the
influence of effective-range corrections in experiment with magnetically
tunable interactions. The level of tuning required could be inside experimental
reach in the near future.Comment: 8 pages, RevTex4 format, 5 figure
GravEn: Software for the simulation of gravitational wave detector network response
Physically motivated gravitational wave signals are needed in order to study
the behaviour and efficacy of different data analysis methods seeking their
detection. GravEn, short for Gravitational-wave Engine, is a MATLAB software
package that simulates the sampled response of a gravitational wave detector to
incident gravitational waves. Incident waves can be specified in a data file or
chosen from among a group of pre-programmed types commonly used for
establishing the detection efficiency of analysis methods used for LIGO data
analysis. Every aspect of a desired signal can be specified, such as start time
of the simulation (including inter-sample start times), wave amplitude, source
orientation to line of sight, location of the source in the sky, etc. Supported
interferometric detectors include LIGO, GEO, Virgo and TAMA.Comment: 10 Pages, 3 Figures, Presented at the 10th Gravitational Wave Data
Analysis Workshop (GWDAW-10), 14-17 December 2005 at the University of Texas,
Brownsvill
Application of “omics” to Prion Biomarker Discovery
The advent of genomics and proteomics has been a catalyst for the discovery of biomarkers able to discriminate biological processes such as the pathogenesis of complex diseases. Prompt detection of prion diseases is particularly desirable given their transmissibility, which is responsible for a number of human health risks stemming from exogenous sources of prion protein. Diagnosis relies on the ability to detect the biomarker PrPSc, a pathological isoform of the host protein PrPC, which is an essential component of the infectious prion. Immunochemical detection of PrPSc is specific and sensitive enough for antemortem testing of brain tissue, however, this is not the case in accessible biological fluids or for the detection of recently identified novel prions with unique biochemical properties. A complementary approach to the detection of PrPSc itself is to identify alternative, “surrogate” gene or protein biomarkers indicative of disease. Biomarkers are also useful to track the progress of disease, especially important in the assessment of therapies, or to identify individuals “at risk”. In this review we provide perspective on current progress and pitfalls in the use of “omics” technologies to screen body fluids and tissues for biomarker discovery in prion diseases
Chi-square test on candidate events from CW signal coherent searches
In a blind search for continuous gravitational wave signals scanning a wide
frequency band one looks for candidate events with significantly large values
of the detection statistic. Unfortunately, a noise line in the data may also
produce a moderately large detection statistic.
In this paper, we describe how we can distinguish between noise line events
and actual continuous wave (CW) signals, based on the shape of the detection
statistic as a function of the signal's frequency. We will analyze the case of
a particular detection statistic, the F statistic, proposed by Jaranowski,
Krolak, and Schutz.
We will show that for a broad-band 10 hour search, with a false dismissal
rate smaller than 1e-6, our method rejects about 70 % of the large candidate
events found in a typical data set from the second science run of the Hanford
LIGO interferometer.Comment: proceedings of GWDAW8, 2003 conference, 12pages, 6 figure
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