54,097 research outputs found
On Integration Methods Based on Scrambled Nets of Arbitrary Size
We consider the problem of evaluating for a function . In situations where
can be approximated by an estimate of the form
, with a point set in
, it is now well known that the Monte Carlo
convergence rate can be improved by taking for the first
points, , of a scrambled
-sequence in base . In this paper we derive a bound for the
variance of scrambled net quadrature rules which is of order
without any restriction on . As a corollary, this bound allows us to provide
simple conditions to get, for any pattern of , an integration error of size
for functions that depend on the quadrature size . Notably,
we establish that sequential quasi-Monte Carlo (M. Gerber and N. Chopin, 2015,
\emph{J. R. Statist. Soc. B, to appear.}) reaches the
convergence rate for any values of . In a numerical study, we show that for
scrambled net quadrature rules we can relax the constraint on without any
loss of efficiency when the integrand is a discontinuous function
while, for sequential quasi-Monte Carlo, taking may only
provide moderate gains.Comment: 27 pages, 2 figures (final version, to appear in The Journal of
Complexity
Cylindric multipartitions and level-rank duality
We show that a multipartition is cylindric if and only if its level rank-dual
is a source in the corresponding affine type crystal. This provides an
algebraic interpretation of cylindricity, and completes a similar result for
FLOTW multipartitions.Comment: 7 pages, 7 figure
When Does Government Limit the Impact of Voter Initiatives?
Citizens use the initiative process to make new laws. Many winning initiatives, however, are altered or ignored after Election Day. We examine why this is, paying particular attention to several widely-ignored properties of the post-election phase of the initiative process. One such property is the fact that initiative implementation can require numerous governmental actors to comply with an initiative’s policy instructions. Knowing such properties, the question then becomes: When do governmental actors comply with winning initiatives? We clarify when compliance is full, partial, or not at all. Our findings provide a template for scholars and observers to better distinguish cases where governmental actors\u27 policy preferences replace initiative content as a determinant of a winning initiative\u27s policy impact from cases where an initiative’s content affects policy despite powerful opponents’ objections. Our work implies that the consequences of this form of democracy are more predictable, but less direct, than often presumed
Review of W and Z Production at the Tevatron
The CDF and \D0 collaborations have used recent data taken at the Tevatron to
perform QCD tests with and bosons decaying leptonically. \D0 measures
the production cross section times branching ratio for and bosons. This
also gives an indirect measurement of the total width of the boson:
\gw=2.126\pm0.092 GeV. CDF reports on a direct measurement of
\gw=2.19\pm0.19 GeV, in good agreement with the indirect determination and
Standard Model predictions. \D0's measurement of the differential
distribution for and bosons decaying to electrons agrees
with the combined QCD perturbative and resummation calculations. In addition,
the distribution for the boson discriminates between
different vector boson production models. Studies of production at CDF
find the NLO QCD prediction for the production rate of events to
be in good agreement with the data.Comment: 8 pages, 6 figures, presented at XXXIIIrd Recontres de Moriond, QCD
AND HIGH ENERGY HADRONIC INTERACTIONS,Les Arcs, Savoie, France, 199
Atom Scattering from Disordered Surfaces in the Sudden Approximation: Double Collisions Effects and Quantum Liquids
The Sudden Approximation (SA) for scattering of atoms from surfaces is
generalized to allow for double collision events and scattering from
time-dependent quantum liquid surfaces. The resulting new schemes retain the
simplicity of the original SA, while requiring little extra computational
effort. The results suggest that inert atom (and in particular He) scattering
can be used profitably to study hitherto unexplored forms of complex surface
disorder.Comment: 15 pages, 1 figure. Related papers available at
http://neon.cchem.berkeley.edu/~dan
He Scattering from Compact Clusters and from Diffusion-Limited Aggregates on Surfaces: Observable Signatures of Structure
The angular intensity distribution of He beams scattered from compact
clusters and from diffusion limited aggregates, epitaxially grown on metal
surfaces, is investigated theoretically. The purpose is twofold: to distinguish
compact cluster structures from diffusion limited aggregates, and to find
observable {\em signatures} that can characterize the compact clusters at the
atomic level of detail. To simplify the collision dynamics, the study is
carried out in the framework of the sudden approximation, which assumes that
momentum changes perpendicular to the surface are large compared with momentum
transfer due to surface corrugation. The diffusion limited aggregates on which
the scattering calculations were done, were generated by kinetic Monte Carlo
simulations. It is demonstrated, by focusing on the example of compact Pt
Heptamers, that signatures of structure of compact clusters may indeed be
extracted from the scattering distribution. These signatures enable both an
experimental distinction between diffusion limited aggregates and compact
clusters, and a determination of the cluster structure. The characteristics
comprising the signatures are, to varying degrees, the Rainbow, Fraunhofer,
specular and constructive interference peaks, all seen in the intensity
distribution. It is also shown, how the distribution of adsorbate heights above
the metal surface can be obtained by an analysis of the specular peak
attenuation. The results contribute to establishing He scattering as a powerful
tool in the investigation of surface disorder and epitaxial growth on surfaces,
alongside with STM.Comment: 41 pages, 16 postscript figures. For more details see
http://www.fh.huji.ac.il/~dan
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