1,425 research outputs found
High Spin Glueballs from the Lattice
We discuss the principles underlying higher spin glueball calculations on the
lattice. For that purpose, we develop numerical techniques to rotate Wilson
loops by arbitrary angles in lattice gauge theories close to the continuum. As
a first application, we compute the glueball spectrum of the SU(2) gauge theory
in 2+1 dimensions for both parities and for spins ranging from 0 up to 4
inclusive. We measure glueball angular wave functions directly, decomposing
them in Fourier modes and extrapolating the Fourier coefficients to the
continuum. This allows a reliable labelling of the continuum states and gives
insight into the way rotation symmetry is recovered. As one of our results, we
demonstrate that the D=2+1 SU(2) glueball conventionally labelled as J^P = 0^-
is in fact 4^- and that the lightest ``J=1'' state has, in fact, spin 3.Comment: Minor changes in the text; the spin 4 glueball mass is taken further
out in Euclidean time at higher beta values. 41 pages, 20 figure
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Mineral Resource Information System for Field Lab in the Osage Mineral Reservation Estate
The Osage Mineral Reservation Estate is located in Osage County, Oklahoma. Minerals on the Estate are owned by members of the Osage Tribe who are shareholders in the Estate. The Estate is administered by the Osage Agency, Branch of Minerals, operated by the U.S. Bureau of Indian Affairs (BIA). Oil, natural gas, casinghead gas, and other minerals (sand, gravel, limestone, and dolomite) are exploited by lessors. Operators may obtain from the Branch of Minerals and the Osage Mineral Estate Tribal Council leases to explore and exploit oil, gas, oil and gas, and other minerals on the Estate. Operators pay a royalty on all minerals exploited and sold from the Estate. A mineral Resource Information system was developed for this project to evaluate the remaining hydrocarbon resources located on the Estate. Databases on Microsoft Excel spreadsheets of operators, leases, and production were designed for use in conjunction with an evaluation spreadsheet for estimating the remaining hydrocarbons on the Estate
Mouse RAD54 affects DNA double-strand break repair and sister chromatid exchange
Cells can achieve error-free repair of DNA double-strand breaks (DSBs) by homologous recombination through gene conversion with or without crossover. In contrast, an alternative homology-dependent DSB repair pathway, single-strand annealing (SSA), results in deletions. In this study, we analyzed the effect of mRAD54, a gene involved in homologous recombination, on the repair of a site-specific I-SceI-induced DSB located in a repeated DNA sequence in the genome of mouse embryonic stem cells. We used six isogenic cell lines differing solely in the orientation of the repeats. The combination of the three recombination-test substrates used discriminated among SSA, intrachromatid gene conversion, and sister chromatid gene conversion. DSB repair was most efficient for the substrate that allowed recovery of SSA events. Gene conversion with crossover, indistinguishable from long tract gene conversion, preferentially involved the sister chromatid rather than the repeat on the same chromatid. Comparing DSB repair in mRAD54 wild-type and knockout cells revealed direct evidence for a role of mRAD54 in DSB repair. The substrate measuring SSA showed an increased efficiency of DSB repair in the absence of mRAD54. The substrate measuring sister chromatid gene conversion showed a decrease in gene conversion with and without crossover. Consistent with this observation, DNA damage-induced sister chromatid exchange was reduced in mRAD54-deficient cells. Our results suggest that mRAD54 promotes gene conversion with predominant use of the sister chromatid as the repair template at the expense of error-prone SSA
Geometrothermodynamics of black holes
The thermodynamics of black holes is reformulated within the context of the
recently developed formalism of geometrothermodynamics. This reformulation is
shown to be invariant with respect to Legendre transformations, and to allow
several equivalent representations. Legendre invariance allows us to explain a
series of contradictory results known in the literature from the use of
Weinhold's and Ruppeiner's thermodynamic metrics for black holes. For the
Reissner-Nordstr\"om black hole the geometry of the space of equilibrium states
is curved, showing a non trivial thermodynamic interaction, and the curvature
contains information about critical points and phase transitions. On the
contrary, for the Kerr black hole the geometry is flat and does not explain its
phase transition structure.Comment: Revised version, to be published in Gen.Rel.Grav.(Mashhoon's
Festschrift
Body Fixed Frame, Rigid Gauge Rotations and Large N Random Fields in QCD
The "body fixed frame" with respect to local gauge transformations is
introduced. Rigid gauge "rotations" in QCD and their \Sch equation are studied
for static and dynamic quarks. Possible choices of the rigid gauge field
configuration corresponding to a nonvanishing static colormagnetic field in the
"body fixed" frame are discussed. A gauge invariant variational equation is
derived in this frame. For large number N of colors the rigid gauge field
configuration is regarded as random with maximally random probability
distribution under constraints on macroscopic--like quantities. For the uniform
magnetic field the joint probability distribution of the field components is
determined by maximizing the appropriate entropy under the area law constraint
for the Wilson loop. In the quark sector the gauge invariance requires the
rigid gauge field configuration to appear not only as a background but also as
inducing an instantaneous quark-quark interaction. Both are random in the large
N limit.Comment: 29 pages LATEX, Weizmann Institute preprint WIS-93/40/Apr -P
Coherent spin valve phenomena and electrical spin injection in ferromagnetic/semiconductor/ferromagnetic junctions
Coherent quantum transport in ferromagnetic/ semiconductor/ ferromagnetic
junctions is studied theoretically within the Landauer framework of ballistic
transport. We show that quantum coherence can have unexpected implications for
spin injection and that some intuitive spintronic concepts which are founded in
semi-classical physics no longer apply: A quantum spin-valve (QSV) effect
occurs even in the absence of a net spin polarized current flowing through the
device, unlike in the classical regime. The converse effect also arises, i.e. a
zero spin-valve signal for a non-vanishing spin-current. We introduce new
criteria useful for analyzing quantum and classical spin transport phenomena
and the relationships between them. The effects on QSV behavior of
spin-dependent electron transmission at the interfaces, interface Schottky
barriers, Rashba spin-orbit coupling and temperature, are systematically
investigated. While the signature of the QSV is found to be sensitive to
temperature, interestingly, that of its converse is not. We argue that the QSV
phenomenon can have important implications for the interpretation of
spin-injection in quantum spintronic experiments with spin-valve geometries.Comment: 15 pages including 11 figures. To appear in PR
The Other Side of Through: Young Breast Cancer Survivors’ Spectrum of Sexual and Reproductive Health Needs
The long-term reproductive health impact of cancer treatments is a concern for premenopausal women with a history of breast cancer. This study examined the unmet sexual and reproductive health needs of breast cancer survivors, as well as concordances and discordances in needs by childbearing status and race. We interviewed 17 women diagnosed with breast cancer between the ages of 18 and 45 years and living in North Carolina. To analyze these data, we used the Sort and Sift, Think and Shift© method, a multidimensional qualitative analysis approach. We learned that breast cancer survivors (a) received limited reproductive health information, (b) desired realistic expectations of conceiving postcancer, (c) struggled with adjusting to their altered physical appearance, and (d) had menopause symptoms that led to sexual health and quality of life issues. Breast cancer survivors are in need of and desire more education and resources to address their sexual and reproductive health concerns
A Non-Abelian Variation on the Savvidy Vacuum of the Yang-Mills Gauge Theory
As a prelude to a truly non-perturbative evaluation of the effective
potential in terms of lattice QCD, the one loop effective potential for a
non-Abelian gauge configuration is calculated using the background field
method. Through a non-trivial correlation between the space and color
orientations the new background field avoids the possible coordinate
singularity, , observed recently by Ken Johnson and his
collaborators in their Schr\"{o}dinger functional study of the SU(2) Yang-Mills
theory. In addition, since our ansatz generates a constant color magnetic field
through the commutator terms rather than derivative terms, many of the
technical drawbacks the Savvidy ansatz suffers on a lattice can be avoided. Our
one loop study yields qualitatively the same result as that of Savvidy's.Comment: 9 pages, preprint BU-HEP-93-2
Optimising ensemble streamflow predictions with bias-correction and data assimilation techniques
This study evaluates the efficacy of bias-correction (BC) and data assimilation (DA) techniques in refining hydrological model predictions. Both approaches are routinely used to enhance hydrological forecasts, yet there have been no studies that have systematically compared their utility. We focus on the application of these techniques to improve operational river flow forecasts in a diverse dataset of 316 catchments in the UK, using the Ensemble Streamflow Prediction (ESP) method applied to the GR4J hydrological model. This framework is used in operational seasonal forecasting, providing a suitable testbed for method application. Assessing the impacts of these two approaches on model performance and forecast skill, we find that BC yields substantial and generalised improvements by rectifying errors post-simulation. Conversely, DA, adjusting model states at the start of the forecast period, provides more subtle enhancements, with the biggest effects seen at short lead times in catchments impacted by snow accumulation/melting processes in winter and spring, and catchments with high Base Flow Index (BFI) during summer months. The choice between BC and DA involves trade-offs, considering conceptual differences, computational demands, and uncertainty handling. Our findings emphasise the need for selective application based on specific scenarios and user requirements. This underscores the potential for developing a selective system (e.g., decision tree) to refine forecasts effectively and deliver user-friendly hydrological predictions. While further work is required to enable implementation, this research contributes insights into the relative strengths and weaknesses of these forecast enhancement methods. These could find application in other forecasting systems, aiding the refinement of hydrological forecasts and meeting the demand for reliable information by end-users
Spin injection into a ballistic semiconductor microstructure
A theory of spin injection across a ballistic
ferromagnet-semiconductor-ferromagnet junction is developed for the Boltzmann
regime. Spin injection coefficient is suppressed by the Sharvin
resistance of the semiconductor , where is the
Fermi-surface cross-section. It competes with the diffusion resistances of the
ferromagnets , and in the absence of contact
barriers. Efficient spin injection can be ensured by contact barriers. Explicit
formulae for the junction resistance and the spin-valve effect are presented.Comment: 5 pages, 2 column REVTeX. Explicit prescription relating the results
of the ballistic and diffusive theories of spin injection is added. To this
end, some notations are changed. Three references added, typos correcte
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