3,750 research outputs found
Economic Impacts of Noxious Facilities: Incorporating the Effects of Risk Aversion
The author suggests an integrative approach for projecting economic impacts of facilities that elicit public Risk aversion. She incorporates both economic stimulus effects and perception-based effects of facilities on the host area economy. Empirical findings are compared and an impact estimation framework is suggested for integrating psychometric and econometric techniques
Radiative pion capture in nuclei: a continuum shell-model approach
The radiative pion capture process in nuclei is approached by using a
continuum shell-model description of the nucleus, together with a
phenomenological treatment of the two particle-two hole effects. It is found
that these effects play an important role to reproduce the observed
experimental photon energy distribution. This distribution as well as the
integrated one depends significantly on the details of the mean field
potential. This makes this process interesting to investigate the nuclear
structure dynamics.Comment: 21 pages, LateX file + 5 figures, epsf.st
Eigenvalue problem in a solid with many inclusions: asymptotic analysis
We construct the asymptotic approximation to the first eigenvalue and
corresponding eigensolution of Laplace's operator inside a domain containing a
cloud of small rigid inclusions. The separation of the small inclusions is
characterised by a small parameter which is much larger compared with the
nominal size of inclusions. Remainder estimates for the approximations to the
first eigenvalue and associated eigenfield are presented. Numerical
illustrations are given to demonstrate the efficiency of the asymptotic
approach compared to conventional numerical techniques, such as the finite
element method, for three-dimensional solids containing clusters of small
inclusions.Comment: 55 pages, 5 figure
Non-localities and Fermi motion corrections in atoms
We evaluate the p-wave amplitudes from the chiral Lagrangians and from
there construct the p-wave part of the nucleus optical potential plus a
small s-wave part induced from the elementary p-wave amplitude and the nuclear
Fermi motion. Simultaneously, the momentum and energy dependence of the s-wave
optical potential, previously developed, are taken into account and shown to
generate a small p-wave correction to the optical potential. All the
corrections considered are small compared to the leading s-wave potential, and
lead to changes in the shifts and widths which are smaller than the
experimental errors.
A thorough study of the threshold region and low densities is conducted,
revealing mathematical problems for which a physical solution is given.Comment: revised version, 28 pages, Latex, 8 postscript figures. Submitted to
Nucl. Phys.
The electromagnetic vertex of neutrinos in an electron background and a magnetic field
We study the electromagnetic vertex function of a neutrino that propagates in
an electron background in the presence of a static magnetic field. The
structure of the vertex function under the stated conditions is determined and
it is written down in terms of a minimal and complete set of tensors. The
one-loop expressions for all the form factors is given, up to terms that are
linear in the magnetic field, and the approximate integral formulas that hold
in the long wavelength limit are obtained. We discuss the physical
interpretation of some of the form factors and their relation with the concept
of the neutrino induced charge. The neutrino acquires a longitudinal and a
transverse charge, due to the fact that the form factors depend on the
transverse and longitudinal components of the photon momentum independently. We
compute those form factors explicitly in various limiting cases and find that
the longitudinal and transverse charge are the same for the case of a
non-relativistic electron gas, but not otherwise.Comment: 18 pages. Revtex4, axodra
X(3872) and its Partners in the Heavy Quark Limit of QCD
In this letter, we propose interpolating currents for the X(3872) resonance,
and show that, in the Heavy Quark limit of QCD, the X(3872) state should have
degenerate partners, independent of its internal structure. Magnitudes of
possible I=0 and I=1 components of the X(3872) are also discussed.Comment: 12 page
Spectral energy distribution analysis of class i and class ii fu orionis stars
FU Orionis stars (FUors) are eruptive pre-main sequence objects thought to represent quasi-periodic or recurring stages of enhanced accretion during the low-mass star-forming process. We characterize the sample of known and candidate FUors in a homogeneous and consistent way, deriving stellar and circumstellar parameters for each object. We emphasize the analysis in those parameters that are supposed to vary during the FUor stage. We modeled the spectral energy distributions of 24 of the 26 currently known FUors, using the radiative transfer code of Whitney et al. We compare our models with those obtained by Robitaille et al. for Taurus class II and I sources in quiescence periods by calculating the cumulative distribution of the different parameters. FUors have more massive disks: we find that ~80% of the disks in FUors are more massive than any Taurus class II and I sources in the sample. Median values for the disk mass accretion rates are ~10–7 M ☉ yr–1 versus ~10–5 M ☉ yr–1 for standard young stellar objects (YSOs) and FUors, respectively. While the distributions of envelope mass accretion rates for class I FUors and standard class I objects are similar, FUors, on average, have higher envelope mass accretion rates than standard class II and class I sources. Most FUors (~70%) have envelope mass accretion rates above 10–7 M ☉ yr–1. In contrast, 60% of the classical YSO sample has an accretion rate below this value. Our results support the current scenario in which changes experimented by the circumstellar disk explain the observed properties of these stars. However, the increase in the disk mass accretion rate is smaller than theoretically predicted, although in good agreement with previous determinations.Fil: Gramajo, Luciana Veronica. Consejo Nacional de Investigaciones CientÃficas y Técnicas; Argentina. Universidad Nacional de Cordoba. Observatorio Astronomico de Cordoba; ArgentinaFil: Rodón Javier A.. European Southern Observatory. Santiago; ChileFil: Gomez, Mercedes Nieves. Consejo Nacional de Investigaciones CientÃficas y Técnicas; Argentina. Universidad Nacional de Cordoba. Observatorio Astronomico de Cordoba; Argentin
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