5,223 research outputs found
Exploring the S-Matrix of Massless Particles
We use the recently proposed generalised on-shell representation for
scattering amplitudes and a consistency test to explore the space of tree-level
consistent couplings in four-dimensional Minkowski spacetime. The extension of
the constructible notion implied by the generalised on-shell representation,
i.e. the possibility to reconstruct at tree level all the scattering amplitudes
from the three-particle ones, together with the imposition of the consistency
conditions at four-particle level, allow to rediscover all the known theories
and their algebra structure, if any. Interestingly, this analysis seems to
leave room for high-spin couplings, provided that at least the requirement of
locality is weakened. We do not claim to have found tree-level consistent
high-spin theories, but rather that our methods show signatures of them and
very likely, with a suitable modification, they can be a good framework to
perform a systematic search.Comment: 44 pages, 1 figur
U(1)-decoupling, KK and BCJ relations in SYM
We proved the color reflection relation, U(1)-decoupling, Kleiss-Kuijf and
Bern-Carrasco-Johansson relation for color-ordered Super
Yang-Mills theory using SYM version BCFW recursion relation,
which depends only on the general properties of super-amplitudes. This verified
the conjectured matter fields BCJ relation. We also show that color reflection
relation and U(1)-decoupling relation are special cases of KK relation, if we
consider the KK relation as a general relation, then the former two relations
come out naturally as the special cases.Comment: 17 page
Resonances from meson-meson scattering in U(3) CHPT
In this work, the complete one loop calculation of meson-meson scattering
amplitudes within U(3)\otimes U(3) chiral perturbation theory with explicit
resonance states is carried out for the first time. Partial waves are
unitarized from the perturbative calculation employing a non-perturbative
approach based on the N/D method. Once experimental data are reproduced in a
satisfactory way we then study the resonance properties, such as the pole
positions, corresponding residues and their N_C behaviors. The resulting N_C
dependence is the first one in the literature that takes into account the fact
that the \eta_1 becomes the ninth Goldstone boson in the chiral limit for large
N_C. Within this scheme the vector resonances studied, \rho(770), K^*(892) and
\phi(1020), follow an N_C trajectory in agreement with their standard \bar{q}q
interpretation. The scalars f_0(1370), a_0(1450) and K^*(1430) also have for
large N_C a \bar{q}q pole position trajectory and all of them tend to a bare
octet of scalar resonances around 1.4 GeV. The f_0(980) tends asymptotically to
the bare pole position of a singlet scalar resonance around 1 GeV. The \sigma,
\kappa and a_0(980) scalar resonances have a very different N_C behavior. The
case of the \sigma resonance is analyzed with special detail.Comment: 50 pages, 15 figures, 1 table. Enlarged version with more detail
comparisons with previous results in the literature. To match with accepted
version for publicatio
Corporate Brand Image: Antecedents, Mediating Role and Impact on Stakeholder Expectations
Corporate identity and image are shaped by the entirety of perceptions of a variety of stakeholders, both existing and potential ones, such as customers, suppliers, employees, general public, opinion makers, and government officials. Our study is an empirical investigation of corporate brand image and impact on one such stakeholder group made up of prospective employees. A large multinational, a technical and scientific research firm, a major recruiter of graduates from campuses of reputable universities across the nation was chosen as the subject. This paper develops and tests a path model of the antecedent factors affecting corporate brand image and specific expectations that stakeholders may have of a corporate brand. Based on a thorough literature review, a corporate brand image model that treated as antecedents the four constructs, awareness of organisation’s products, perceptions about culture, personality of the focal firm, and general expectations was proposed. Specific expectations that respondents may have about working with the firm was modeled to be influenced by the corporate brand image of the firm surveyed and also by the mentioned four antecedent constructs. The model is fitted to empirical data obtained from a national sample of 368 respondents using LISREL 8.5 methodology, and strong support was found for five, partial support for two of the nine hypotheses tested. Substantial evidence can be seen for the mediating role of corporate brand image in shaping specific expectations that stakeholders have from the corporate brand. Practical significance and managerial implications for marketing investments and organisational performance are detailed.
Trapping cold atoms near carbon nanotubes: thermal spin flips and Casimir-Polder potential
We investigate the possibility to trap ultracold atoms near the outside of a
metallic carbon nanotube (CN) which we imagine to use as a miniaturized
current-carrying wire. We calculate atomic spin flip lifetimes and compare the
strength of the Casimir-Polder potential with the magnetic trapping potential.
Our analysis indicates that the Casimir-Polder force is the dominant loss
mechanism and we compute the minimum distance to the carbon nanotube at which
an atom can be trapped.Comment: 8 pages, 3 figure
Measuring longitudinal amplitudes for electroproduction of pseudoscalar mesons using recoil polarization in parallel kinematics
We propose a new method for measuring longitudinal amplitudes for
electroproduction of pseudoscalar mesons that exploits a symmetry relation for
polarization observables in parallel kinematics. This polarization technique
does not require variation of electron scattering kinematics and avoids the
major sources of systematic errors in Rosenbluth separation.Comment: intended for Phys. Rev. C as a Brief Repor
Quasifree pion photoproduction on the deuteron in the region
Photo production of pions on the deuteron is studied in the spectator nucleon
model. The Born terms of the elementary production amplitude are determined in
pseudovector N coupling and supplied with a form factor. The
resonance is considered both in the and the channel. The parameters of
the resonance and the cutoff of the form factors are fixed on the
leading photoproduction multipoles. Results for total and differential cross
sections are compared with experimental data. Particular attention is paid to
the role of Pauli correlations of the final state nucleons in the quasifree
case. The results are compared with those for pion photoproduction on the
nucleon.Comment: 17 pages LateX2e including 5 postscript figure
The application of fluid dynamic gauging in characterising cake deposition during the cross-flow microfiltration of a yeast suspension
Widespread pain and depression are key modifiable risk factors associated with reduced social participation in older adults: A prospective cohort study in primary care.
In older adults, reduced social participation increases the risk of poor health-related quality of life, increased levels of inflammatory markers and cardiovascular disease, and increased mortality. Older adults frequently present to primary care, which offers the potential to deliver interventions at the point of care to increase social participation. The aim of this prospective study was to identify the key modifiable exposures that were associated with reduced social participation in a primary care population of older adults.The study was a population-based prospective cohort study. Participants (n = 1991) were those aged ≥65 years who had completed questionnaires at baseline, and 3 and 6-year follow-ups. Generalized linear mixed modeling framework was used to test for associations between exposures and decreasing social participation over 6 years.At baseline, 44% of participants reported reduced social participation, increasing to 49% and 55% at 3 and 6-year follow-up. Widespread pain and depression had the strongest independent association with reduced social participation over the 6-year follow-up period. The prevalence of reduced social participation for those with widespread pain was 106% (adjusted incidence rate ratio 2.06, 95% confidence interval 1.72, 2.46), higher than for those with no pain. Those with depression had an increased prevalence of 82% (adjusted incidence rate ratio 1.82, 95% confidence interval 1.62, 2.06). These associations persisted in multivariate analysis.Population ageing will be accompanied by increasing numbers of older adults with pain and depression. Future trials should assess whether screening for widespread pain and depression, and targeting appropriate treatment in primary care, increase social participation in older people
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