9,167 research outputs found
Probing the topological structure of the QCD vacuum with overlap fermions
Overlap fermions implement exact chiral symmetry on the lattice and are thus
an appropriate tool for investigating the chiral and topological structure of
the QCD vacuum. We study various chiral and topological aspects on
Luescher-Weisz-type quenched gauge field configurations using overlap fermions
as a probe. Particular emphasis is placed upon the analysis of the spectral
density and the localisation properties of the eigenmodes as well as on the
local structure of topological charge fluctuations.Comment: 8 pages, 6 figures, talk given at the Workshop on Computational
Hadron Physics, Nicosia, Cyprus, September 14-17, 2005; v2: Fig.6 corrected,
statistics in Fig. 4-6 increased, minor text change
Independent sexual violence advisers (ISVAs) in England, Wales and Northern Ireland: a study of impacts, effects, coping mechanisms and effective support systems for people working as ISVAs and ISVA Managers
This study is the first of its kind in England, Wales and Northern Ireland and was carried out to gather information about the impact of working as Independent Sexual Violence Advisers (ISVAs) or ISVA Managers. The ISVA role is relatively new, and as such, little is known about this difficult and emotionally charged work. Although some literature looks at the impact of working in the sexual violence field, there is little from England, Wales or Northern Ireland, and even less focused on the direct, ongoing, face-to-face work ISVAs do. This report focuses on the impacts, effects, coping mechanisms and effective support systems for people working as ISVAs and ISVA Managers in supporting victim-survivors of sexual violence across England, Wales and Northern Ireland. Since its introduction in 2005, the ISVA role has been invaluable in providing continuous support to victim-survivors of sexual violence and working to meet their emotional and practical needs during the criminal justice process. As conviction rates are at an all-time low, ISVAs can also provide support to people who may otherwise feel let down by the Criminal Justice System. ISVAs can also support people who do not want to report the crime to the police – helping people at, potentially, the lowest point of their life. This survey focused on providing an overview of the ISVA role (e.g. context they work in, caseloads, supervision and support available) and determining which factors predict the likelihood of experiencing negative and positive impacts as a result of the work they do
Color-flavor locked strange matter
We analyze how the CFL states in dense matter work in the direction of
enhancing the parameter space for absolutely stable phases (strange matter). We
find that the "CFL strange matter" phase can be the true ground state of
hadronic matter for a much wider range of the parameters of the model (the gap
of the QCD Cooper pairs , the strange quark mass and the Bag
Constant ) than the state without any pairing, and derive a full equation of
state and an accurate analytic approximation to the lowest order in
and which may be directly used for applications. The effects of pairing
on the equation of state are found to be small (as previously expected) but not
negligible and may be relevant for astrophysics.Comment: 5 pages, 2 figure
Overlap Valence on 2+1 Flavor Domain Wall Fermion Configurations with Deflation and Low-mode Substitution
The overlap fermion propagator is calculated on 2+1 flavor domain wall
fermion gauge configurations on 16^3 x 32, 24^3 x 64 and 32^3 x 64 lattices.
With HYP smearing and low eigenmode deflation, it is shown that the inversion
of the overlap operator can be expedited by ~ 20 times for the 16^3 x 32
lattice and ~ 80 times for the 32^3 x 64 lattice. Through the study of
hyperfine splitting, we found that the O(m^2a^2) error is small and these
dynamical fermion lattices can adequately accommodate quark mass up to the
charm quark. The low energy constant \Delta_{mix} which characterizes the
discretization error of the pion made up of a pair of sea and valence quarks in
this mixed action approach is calculated via the scalar correlator with
periodic and anti-periodic boundary conditions. It is found to be small which
shifts a 300 MeV pion mass by ~ 10 to 19 MeV on these sets of lattices. We have
studied the signal-to-noise issue of the noise source for the meson and baryon.
It is found that the many-to-all meson and baryon correlators with Z_3 grid
source and low eigenmode substitution is efficient in reducing errors for the
correlators of both mesons and baryons. With 64-point Z_3 grid source and
low-mode substitution, it can reduce the statistical errors of the light quark
(m_{\pi} ~ 200 - 300 MeV) meson and nucleon correlators by a factor of ~ 3-4 as
compared to the point source. The Z_3 grid source itself can reduce the errors
of the charmonium correlators by a factor of ~ 3.Comment: 30 pages, 18 figures, replaced with the version to be published in
PR
A quantitative metric for the comparative evaluation of optical clearing protocols for 3D multicellular spheroids
3D multicellular spheroids quickly emerged as in vitro models because they represent the in vivo tumor environment better than standard 2D cell cultures. However, with current microscopy technologies, it is difficult to visualize individual cells in the deeper layers of 3D samples mainly because of limited light penetration and scattering. To overcome this problem several optical clearing methods have been proposed but defining the most appropriate clearing approach is an open issue due to the lack of a gold standard metric. Here, we propose a guideline for 3D light microscopy imaging to achieve single-cell resolution. The guideline includes a validation experiment focusing on five optical clearing protocols. We review and compare seven quality metrics which quantitatively characterize the imaging quality of spheroids. As a test environment, we have created and shared a large 3D dataset including approximately hundred fluorescently stained and optically cleared spheroids. Based on the results we introduce the use of a novel quality metric as a promising method to serve as a gold standard, applicable to compare optical clearing protocols, and decide on the most suitable one for a particular experiment
A Perturbative Study of a General Class of Lattice Dirac Operators
A perturbative study of a general class of lattice Dirac operators is
reported, which is based on an algebraic realization of the Ginsparg-Wilson
relation in the form
where stands for a non-negative integer.
The choice corresponds to the commonly discussed Ginsparg-Wilson relation
and thus to the overlap operator. We study one-loop fermion contributions to
the self-energy of the gauge field, which are related to the fermion
contributions to the one-loop function and to the Weyl anomaly. We
first explicitly demonstrate that the Ward identity is satisfied by the
self-energy tensor. By performing careful analyses, we then obtain the correct
self-energy tensor free of infra-red divergences, as a general consideration of
the Weyl anomaly indicates. This demonstrates that our general operators give
correct chiral and Weyl anomalies. In general, however, the Wilsonian effective
action, which is supposed to be free of infra-red complications, is expected to
be essential in the analyses of our general class of Dirac operators for
dynamical gauge field.Comment: 30 pages. Some of the misprints were corrected. Phys. Rev. D (in
press
Multidisciplinary research from ERTS-1 data
There are no author-identified significant results in this report
Detection of ultra-high energy cosmic ray showers with a single-pixel fluorescence telescope
We present a concept for large-area, low-cost detection of ultra-high energy
cosmic rays (UHECRs) with a Fluorescence detector Array of Single-pixel
Telescopes (FAST), addressing the requirements for the next generation of UHECR
experiments. In the FAST design, a large field of view is covered by a few
pixels at the focal plane of a mirror or Fresnel lens. We report first results
of a FAST prototype installed at the Telescope Array site, consisting of a
single 200 mm photomultiplier tube at the focal plane of a 1 m Fresnel lens
system taken from the prototype of the JEM-EUSO experiment. The FAST prototype
took data for 19 nights, demonstrating remarkable operational stability. We
detected laser shots at distances of several kilometres as well as 16 highly
significant UHECR shower candidates.Comment: Accepted for publication in Astroparticle Physic
Use of ERTS-1 data: Summary report of work on ten tasks
The author has identified the following significant results. Depth mapping's for a portion of Lake Michigan and at the Little Bahama Bank test site have been verified by use of navigation charts and on-site visits. A thirteen category recognition map of Yellowstone Park has been prepared. Model calculation of atmospheric effects for various altitudes have been prepared. Radar, SLAR, and ERTS-1 data for flooded areas of Monroe County, Michigan are being studied. Water bodies can be reliably recognized and mapped using maximum likelihood processing of ERTS-1 digital data. Wetland mapping has been accomplished by slicing of single band and/or ratio processing of two bands for a single observation date. Both analog and digital processing have been used to map the Lake Ontario basin using ERTS-1 data. Operating characteristic curves were developed for the proportion estimation algorithm to determine its performance in the measurement of surface water area. The signal in band MSS-5 was related to sediment content of waters by modelling approach and by relating surface measurements of water to processed ERTS data. Radiance anomalies in ERTS-1 data could be associated with the presence of oil on water in San Francisco Bay, but the anomalies were of the same order as those caused by variations in sediment concentration and tidal flushing
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