2,689 research outputs found
Threshold Factorization Redux
We reanalyze the factorization theorems for Drell-Yan process and for deep
inelastic scattering near threshold, as constructed in the framework of the
soft-collinear effective theory (SCET), from a new, consistent perspective. In
order to formulate the factorization near threshold in SCET, we should include
an additional degree of freedom with small energy, collinear to the beam
direction. The corresponding collinear-soft mode is included to describe the
parton distribution function (PDF) near threshold. The soft function is
modified by subtracting the contribution of the collinear-soft modes in order
to avoid double counting on the overlap region. As a result, the proper soft
function becomes infrared finite, and all the factorized parts are free of
rapidity divergence. Furthermore, the separation of the relevant scales in each
factorized part becomes manifest. We apply the same idea to the dihadron
production in annihilation near threshold, and show that the
resultant soft function is also free of infrared and rapidity divergences.Comment: 20 pages, 2 figures; matches published versio
Small and Large Scale Granular Statics
Recent experimental results on the static or quasistatic response of granular
materials have been interpreted to suggest the inapplicability of the
traditional engineering approaches, which are based on elasto-plastic models
(which are elliptic in nature). Propagating (hyperbolic) or diffusive
(parabolic) models have been proposed to replace the `old' models. Since
several recent experiments were performed on small systems, one should not
really be surprised that (continuum) elasticity, a macroscopic theory, is not
directly applicable, and should be replaced by a grain-scale (``microscopic'')
description. Such a description concerns the interparticle forces, while a
macroscopic description is given in terms of the stress field. These
descriptions are related, but not equivalent, and the distinction is important
in interpreting the experimental results. There are indications that at least
some large scale properties of granular assemblies can be described by
elasticity, although not necessarily its isotropic version. The purely
repulsive interparticle forces (in non-cohesive materials) may lead to
modifications of the contact network upon the application of external forces,
which may strongly affect the anisotropy of the system. This effect is expected
to be small (in non-isostatic systems) for small applied forces and for
pre-stressed systems (in particular for disordered systems). Otherwise, it may
be accounted for using a nonlinear, incrementally elastic model, with
stress-history dependent elastic moduli. Although many features of the
experiments may be reproduced using models of frictionless particles, results
demonstrating the importance of accounting for friction are presented.Comment: 10 pages, 9 figures. Accepted for publication in "Granular Matter"
(special issue: 4th Int. Conf. on Conveying and Handling of Particulate
Solids, Budapest, Hungary, May 2003). v2: Minor revisions to text and figure
Student Perceptions of Engagement in a Mandatory Programatic Service Learning
In the hospitality industry, service-learning opportunities are particularly important for students seeking work in the meeting and event planning industry. Faculty of a hospitality program at a regional university in East Texas decided to investigate the benefits in embedding service learning activities to their hospitality courses. The study investigated student perceptions of their participation in compulsory service learning assignments were created and implemented. Service learning assignment benefited the respondents personally; it benefited the sponsoring organization; it benefited the respondents’ career goals and their own individual awareness of community issues
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