17,668 research outputs found
Ising instability of a Holstein phonon mode in graphene
We study the thermal distribution of phonons in a graphene sheet. Due to the
two electronic bands there are two out-of-plane phonon modes with respect to
the two sublattices. One of these modes undergoes an Ising transition by
spontaneously breaking the sublattice symmetry. We calculate the critical
point, the renormalization of the phonon frequency and the average lattice
distortion. This transition might be observable in Raman scattering and in
transport properties.Comment: 5 pages, 2 figure
Next-nearest-neighbor Tight-binding Model of Plasmons in Graphene
In this paper we investigate the influence of the next-nearest-neighbor
coupling of tight-binding model of graphene on the spectrum of plasmon
excitations. The nearest-neighbor tight-binding model was previously used to
calculate plasmon spectrum in the next paper [1]. We expand the previous
results of the paper by the next-nearest-neighbor tight-binding model. Both
methods are based on the numerical calculation of the dielectric function of
graphene and loss function. Here we compare plasmon spectrum of the
next-nearest and nearest-neighbor tight-binding models and find differences
between plasmon dispersion of two models.Comment: LaTeX, 4 pages, 4 Fig
Estimating Water Demand Schedules for Selected Industries in Arkansas
Water demand functions for the paper and chemical industries in the state of Arkansas were estimated utilizing data collected from individual plants throughout the state. Regression analysis was used to estimate demand functions from a data base which included information on intake and gross water use by source, recirculated water use, costs of acquiring, treating, and discharging water, plant output, employment, and level of technology. The demand for intake water was estimated as an exponential function of average water costs and the level of technology primarily. Price elasticities of demand were estimated as approximately equal to one for both industries. The results of this study could be used to determine the effects of various public policies on the withdrawal of water for industrial purposes
RELIABILITY OF OPTIONS MARKETS FOR CROP REVENUE INSURANCE RATING
Revenue insurance, only recently introduced for major crops in the U.S., has captured a considerable share of the multiple-peril insurance market. This study evaluates the predictive reliability of using price distributions inferred from options markets to rate revenue insurance products. We find for periods early in the crop growing season that price distributions inferred from options trades offer greater reliability than distributions based on historical futures trades. Options-based price distributions should receive further consideration in crop revenue insurance rating, but current administrative constraints must be considered.Risk and Uncertainty,
Vertex-Facet Incidences of Unbounded Polyhedra
How much of the combinatorial structure of a pointed polyhedron is contained
in its vertex-facet incidences? Not too much, in general, as we demonstrate by
examples. However, one can tell from the incidence data whether the polyhedron
is bounded. In the case of a polyhedron that is simple and "simplicial," i.e.,
a d-dimensional polyhedron that has d facets through each vertex and d vertices
on each facet, we derive from the structure of the vertex-facet incidence
matrix that the polyhedron is necessarily bounded. In particular, this yields a
characterization of those polyhedra that have circulants as vertex-facet
incidence matrices.Comment: LaTeX2e, 14 pages with 4 figure
Prospects for Measuring from Jets at HERA with Polarized Protons
The measurement of the polarized gluon distribution function
from photon gluon fusion processes in electron proton deep inelastic scattering
producing two jets has been investigated. The study is based on the MEPJET
simulation program. The size of the expected spin asymmetry and corresponding
statistical uncertainties for a possible measurement with polarized beams of
electrons and protons at HERA have been estimated. The results show that the
asymmetry can reach a few percents.Comment: 8 pages (Latex) plus 3 figures enclosed as a uuencoded postscript
file. The complete paper, including figures, is also available via anonymous
ftp at ftp://www-ttp.physik.uni-karlsruhe.de/ , or via www at
http://www-ttp.physik.uni-karlsruhe.de/cgi-bin/preprints
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