10,975 research outputs found
Baryon Self-Energy With QQQ Bethe-Salpeter Dynamics In The Non-Perturbative QCD Regime: n-p Mass Difference
A qqq BSE formalism based on DB{\chi}S of an input 4-fermion Lagrangian of
`current' u,d quarks interacting pairwise via gluon-exchange-propagator in its
{\it non-perturbative} regime, is employed for the calculation of baryon
self-energy via quark-loop integrals. To that end the baryon-qqq vertex
function is derived under Covariant Instantaneity Ansatz (CIA), using Green's
function techniques. This is a 3-body extension of an earlier q{\bar q}
(2-body) result on the exact 3D-4D interconnection for the respective BS wave
functions under 3D kernel support, precalibrated to both q{\bar q} and qqq
spectra plus other observables. The quark loop integrals for the neutron (n) -
proton (p) mass difference receive contributions from : i) the strong SU(2)
effect arising from the d-u mass difference (4 MeV); ii) the e.m. effect of the
respective quark charges. The resultant n-p difference comes dominantly from
d-u effect (+1.71 Mev), which is mildly offset by e.m.effect (-0.44), subject
to gauge corrections. To that end, a general method for QED gauge corrections
to an arbitrary momentum dependent vertex function is outlined, and on on a
proportionate basis from the (two-body) kaon case, the net n-p difference works
out at just above 1 MeV. A critical comparison is given with QCD sum rules
results.Comment: be 27 pages, Latex file, and to be published in IJMPA, Vol 1
3D-4D Interlinkage Of qqq Wave Functions Under 3D Support For Pairwise Bethe-Salpeter Kernels
Using the method of Green's functions within a Bethe-Salpeter framework
characterized by a pairwise qq interaction with a Lorentz-covariant 3D support
to its kernel, the 4D BS wave function for a system of 3 identical relativistic
spinless quarks is reconstructed from the corresponding 3D form which satisfies
a fully connected 3D BSE. This result is a 3-body generalization of a similar
2-body result found earlier under identical conditions of a 3D support to the
corresponding qq-bar BS kernel under Covariant Instaneity (CIA for short). (The
generalization from spinless to fermion quarks is straightforward).
To set the CIA with 3D BS kernel support ansatz in the context of
contemporary approaches to the qqq baryon problem, a model scalar 4D qqq BSE
with pairwise contact interactions to simulate the NJL-Faddeev equations is
worked out fully, and a comparison of both vertex functions shows that the CIA
vertex reduces exactly to the NJL form in the limit of zero spatial range. This
consistency check on the CIA vertex function is part of a fuller accounting for
its mathematical structure whose physical motivation is traceable to the role
of `spectroscopy' as an integral part of the dynamics.Comment: 20 pages, Latex, submitted via the account of K.-C. Yan
Quasi-reversible Magnetoresistance in Exchange Spring Tunnel Junctions
We report a large, quasi-reversible tunnel magnetoresistance in
exchange-biased ferromagnetic semiconductor tunnel junctions wherein a soft
ferromagnetic semiconductor (\gma) is exchange coupled to a hard ferromagnetic
metal (MnAs). Our observations are consistent with the formation of a region of
inhomogeneous magnetization (an "exchange spring") within the biased \gma
layer. The distinctive tunneling anisotropic magnetoresistance of \gma produces
a pronounced sensitivity of the magnetoresistance to the state of the exchange
spring
Disability Identification Cards: Issues in Effective Design
Around the world, the issue of disability inclusion is gaining increasing prominence. To promote disability-inclusion in programmes, a growing number of countries are considering the creation of a disability identification card. However, the administration of a disability ID card in low and middle-income countries differs from those in high-income countries. The purpose of this article is to discuss some of the challenges involved in creating a disability ID and how to address these challenges in the context of low and middle-income countries, suggesting that countries considering instituting disability ID cards must move with caution. ID card programmes can only advance disability policy and the wellbeing of persons with disabilities if undertaken in a well-designed manner in line with a country’s administrative capacity
Extra costs of living with a disability: A review and agenda for research
BACKGROUND: There has been a growing interest in disability and poverty on the international research and policy stages. Poverty assessments for persons with disabilities may be affected by the experience of extra costs associated with a disability. OBJECTIVE: This article provides a systematized review of the global literature on the direct costs associated with living with a disability at the individual or household level. METHODS: We searched three databases for peer-reviewed journal articles that estimated extra costs associated with disability: Econlit, SocIndex and PubMed. RESULTS: We found 20 such studies conducted in 10 countries. These studies were predominantly from high-income countries. Although studies were heterogeneous (e.g., in terms of disability measures and cost methodologies), estimated costs were sizeable and some patterns were consistent across studies. Costs varied according to the severity of disability, life cycle and household composition. Highest costs were observed among persons with severe disabilities, and among persons with disabilities living alone or in small sized households. CONCLUSIONS: More quantitative evidence is needed using rigorous methods, for instance evidence based on longitudinal data and as part of policy evaluations. More internationally comparable data on disability is required for the quantitative evidence to develop, especially in low- and middle-income countries where studies are scarce. Qualitative and participatory research is also needed, especially to investigate unmet needs, and the consequences of extra costs
{CurveFusion}: {R}econstructing Thin Structures from {RGBD} Sequences
We introduce CurveFusion, the first approach for high quality scanning of thin structures at interactive rates using a handheld RGBD camera. Thin filament-like structures are mathematically just 1D curves embedded in R^3, and integration-based reconstruction works best when depth sequences (from the thin structure parts) are fused using the object's (unknown) curve skeleton. Thus, using the complementary but noisy color and depth channels, CurveFusion first automatically identifies point samples on potential thin structures and groups them into bundles, each being a group of a fixed number of aligned consecutive frames. Then, the algorithm extracts per-bundle skeleton curves using L1 axes, and aligns and iteratively merges the L1 segments from all the bundles to form the final complete curve skeleton. Thus, unlike previous methods, reconstruction happens via integration along a data-dependent fusion primitive, i.e., the extracted curve skeleton. We extensively evaluate CurveFusion on a range of challenging examples, different scanner and calibration settings, and present high fidelity thin structure reconstructions previously just not possible from raw RGBD sequences
The Economic Lives of People with Disabilities in Vietnam
Through a series of focus group discussions conducted in northern and central Vietnam, this study gives voice to the lived economic experience of families with disabilities and how they manage the economic challenges associated with disability. The dynamic of low and unstable income combined with on-going health care and other disability-related costs gives rise to a range of coping mechanisms (borrowing, reducing and foregoing expenditures, drawing upon savings and substituting labour) that helps to maintain living standards in the short-run yet threatens the longer-term welfare of both the individual with disability and their household. Current social protection programs were reported as not accessible to all and while addressing some immediate economic costs of disability, do not successfully meet current needs nor accommodate wider barriers to availing benefits
Coexistence of Band Jahn Teller Distortion and superconductivity in correlated systems
The co-existence of band Jahn-Teller (BJT) effect with superconductivity (SC)
is studied for correlated systems, with orbitally degenerate bands using a
simple model. The Hubbard model for a doubly degenerate orbital with the
on-site intraorbital Coulomb repulsion treated in the slave boson formalism and
the interorbital Coulomb repulsion treated in the Hartree-Fock mean field
approximation, describes the correlated system. The model further incorporates
the BJT interaction and a pairing term to account for the lattice distortion
and superconductivity respectively. It is found that structural distortion
tends to suppress superconductivity and when SC sets in at low temperatures,
the growth of the lattice distortion is arrested. The phase diagram comprising
of the SC and structural transition temperatures and versus the
dopant concentration reveals that the highest obtainable for an
optimum doping is limited by structural transition. The dependence of the
occupation probabilities of the different bands as well as the density of
states (DOS) in the distorted-superconducting phase, on electron correlation
has been discussed.Comment: RevTex, 4 pages, 4 figuers (postscript files attached) Journal
Reference : Phys. Rev. B (accepted for publication
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