6,620 research outputs found
Are there S=-2 Pentaquarks?
Recent evidence for pentaquark baryons in the channels ,
and their anti-particles claimed by the NA49 collaboration is
critically confronted with the vast amount of existing data on
spectroscopy which was accumulated over the past decades. It is shown that the
claim is at least partially inconsistent with these data. In addition two
further exotic channels of the pentaquark type available in the NA49 data are
investigated. It is argued that this study leads to internal inconsistency with
the purported signals
Momentum Space Integral Equations for Three Charged Particles: Diagonal Kernels
It has been a long-standing question whether momentum space integral
equations of the Faddeev type are applicable to reactions of three charged
particles, in particular above the three-body threshold. For, the presence of
long-range Coulomb forces has been thought to give rise to such severe
singularities in their kernels that the latter may lack the compactness
property known to exist in the case of purely short-range interactions.
Employing the rigorously equivalent formulation in terms of an
effective-two-body theory we have proved in a preceding paper [Phys. Rev. C
{\bf 61}, 064006 (2000)] that, for all energies, the nondiagonal kernels
occurring in the integral equations which determine the transition amplitudes
for all binary collision processes, possess on and off the energy shell only
integrable singularities, provided all three particles have charges of the same
sign, i.e., all Coulomb interactions are repulsive. In the present paper we
prove that, for particles with charges of equal sign, the diagonal kernels, in
contrast, possess one, but only one, nonintegrable singularity. The latter can,
however, be isolated explicitly and dealt with in a well-defined manner. Taken
together these results imply that modified integral equations can be
formulated, with kernels that become compact after a few iterations. This
concludes the proof that standard solution methods can be used for the
calculation of all binary (i.e., (in-)elastic and rearrangement) amplitudes by
means of momentum space integral equations of the effective-two-body type.Comment: 36 pages, 2 figures, accepted for publication in Phys. Rev.
Cold Atom Physics Using Ultra-Thin Optical Fibers: Light-Induced Dipole Forces and Surface Interactions
The strong evanescent field around ultra-thin unclad optical fibers bears a
high potential for detecting, trapping, and manipulating cold atoms.
Introducing such a fiber into a cold atom cloud, we investigate the interaction
of a small number of cold Caesium atoms with the guided fiber mode and with the
fiber surface. Using high resolution spectroscopy, we observe and analyze
light-induced dipole forces, van der Waals interaction, and a significant
enhancement of the spontaneous emission rate of the atoms. The latter can be
assigned to the modification of the vacuum modes by the fiber.Comment: 4 pages, 4 figure
Geometric approach to nonvariational singular elliptic equations
In this work we develop a systematic geometric approach to study fully
nonlinear elliptic equations with singular absorption terms as well as their
related free boundary problems. The magnitude of the singularity is measured by
a negative parameter , for , which reflects on
lack of smoothness for an existing solution along the singular interface
between its positive and zero phases. We establish existence as well sharp
regularity properties of solutions. We further prove that minimal solutions are
non-degenerate and obtain fine geometric-measure properties of the free
boundary . In particular we show sharp
Hausdorff estimates which imply local finiteness of the perimeter of the region
and a.e. weak differentiability property of
.Comment: Paper from D. Araujo's Ph.D. thesis, distinguished at the 2013 Carlos
Gutierrez prize for best thesis, Archive for Rational Mechanics and Analysis
201
Impactos Do Engajamento Das Empresas Com Seus Stakeholders [The Impacts of Stakeholder Engagement]
This empirical paper explores mechanisms by which stakeholders are granted a voice in corporate decision-making processes. A systematic analysis of stakeholder engagement of 51 companies participating in UK’s Business in the Community’s Corporate Responsibility Index is presented, showing the type of stakeholders companies engage with, by which means, as well as the impact of such engagement. We found that leading firms are moving from risk- to opportunity-based engagement using open and long-term engagement mechanisms to align their decisions with their stakeholders’ views and concerns. As results indicate that companies are granting stakeholder views to shape important governance aspects such as policies as well as monitoring and measuring progress, we propagate the term stakeholder governance for advanced forms of stakeholder engagement
Generalized thermodynamic uncertainty relations
We analyze ensemble in which energy (E), temperature (T) and multiplicity (N)
can all fluctuate and with the help of nonextensive statistics we propose a
relation connecting all fluctuating variables. It generalizes Lindhard's
thermodynamic uncertainty relations known in literature.Comment: 13 pages, 2 figures, version to occur in Physica A (2011);
doi:10.1016/j.physa.2011.05.00
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