17,605 research outputs found
Optimal Summation and Integration by Deterministic, Randomized, and Quantum Algorithms
We survey old and new results about optimal algorithms for summation of
finite sequences and for integration of functions from Hoelder or Sobolev
spaces. First we discuss optimal deterministic and randomized algorithms. Then
we add a new aspect, which has not been covered before on conferences about
(quasi-) Monte Carlo methods: quantum computation. We give a short introduction
into this setting and present recent results of the authors on optimal quantum
algorithms for summation and integration. We discuss comparisons between the
three settings. The most interesting case for Monte Carlo and quantum
integration is that of moderate smoothness k and large dimension d which, in
fact, occurs in a number of important applied problems. In that case the
deterministic exponent is negligible, so the n^{-1/2} Monte Carlo and the
n^{-1} quantum speedup essentially constitute the entire convergence rate. We
observe that -- there is an exponential speed-up of quantum algorithms over
deterministic (classical) algorithms, if k/d tends to zero; -- there is a
(roughly) quadratic speed-up of quantum algorithms over randomized classical
algorithms, if k/d is small.Comment: 13 pages, contribution to the 4th International Conference on Monte
Carlo and Quasi-Monte Carlo Methods, Hong Kong 200
The National Wealth of Selected Countries - A Descriptive Essay
What determines the wealth of nations? If anyone knew the answer to that question, no-one would have heard of Adam Smith as an economist, and for that matter all economists. Economics is really the study of wealth creation under scarcity. The reason economists and others have a hard time pinning down the causes of wealth is that wealth is costly to measure, and many factors and forces are potential determinants. This paper describes, in a simple way, wealth accounting by extending the data assembled by a recent World Bank study. The extension will benefit those seeking to run time-series, cross-section, and/or pooled data regressions to assess how wealth is determined. But even from this simple data mining exercise alone the results indicate significant increases in the wealth of the 92 countries in this sample. From the theoretical standpoint the World Bank’s expanded measure under-estimates the wealth of developing countries. Yet, even if the income (GDP) component of their wealth has fallen, total national wealth has increased. The policy implications of this essay are tentative until empirical analysis is carried; even so, the results seem to suggest that GDP is a necessary but not a sufficient requirement for wealth.national wealth; Alfred Marshall on wealth, estimating wealth, World Bank’s national wealth estimating
Exchange coupling between magnetic layers across non-magnetic superlattices
The oscillation periods of the interlayer exchange coupling are investigated
when two magnetic layers are separated by a metallic superlattice of two
distinct non-magnetic materials. In spite of the conventional behaviour of the
coupling as a function of the spacer thickness, new periods arise when the
coupling is looked upon as a function of the number of cells of the
superlattice. The new periodicity results from the deformation of the
corresponding Fermi surface, which is explicitly related to a few controllable
parameters, allowing the oscillation periods to be tuned.Comment: 13 pages; 5 figures; To appear in J. Phys.: Cond. Matte
Growth of single and multilayer sesquioxide crystal films for lasing applications via pulsed laser deposition
Sesquioxides, materials of the form RE2O3 (RE: rare earth), are of great interest for lasing applications. These materials offer high thermal conductivities, are mechanically stable, can easily be doped with various rare earth ions and are optically isotropic. Members of the sesquioxide family have the same crystal structure but differing refractive indices, and hence are ideal candidates for multilayer as well as single film growth. Sesquioxides can be challenging to grow from the melt, however, due to their high melting points (>2400 °C)
NNLO predictions for Z-boson pair production at the LHC
We present a calculation of the NNLO QCD corrections to Z-boson pair
production at hadron colliders, based on the N-jettiness method for the real
radiation parts. We discuss the size and shape of the perturbative corrections
along with their associated scale uncertainties and compare our results to
recent LHC data at TeV.Comment: 19 pages, 2 Tables, 4 figures. Version to appear in JHE
A discrete particle simulation study on the influence of restitution coefficient on spout fluidized bed dynamics
In this paper the influence of the normal restitution coefficient on the bed dynamics\ud
during different flow regimes was studied using the discrete element model. The three flow\ud
regimes comprise the intermediate/spout-fluidization, spouting-with-aeration regime and the jetin-\ud
fluidized-bed. It is shown that with increase of the restitution coefficient the average bed\ud
height decreases for all flow regime cases. To study the influence of the granule impact velocity\ud
and the liquid film on the wall surface the free-fall experiments in the velocity range of 0.5-\ud
4.5 m/s were performed with spherical γ-Al2O3 granules. During the free-fall tests, the impact\ud
angle from 0° to 80° and the viscosity of thin liquid film in the range of 1-300 mPa·s were\ud
varied
The anomeric specificity of yeast galactokinase
Anomeric specificity of yeast galactokinase by chromatographic method
Numerical evaluation of two-loop integrals with pySecDec
We describe the program pySecDec, which factorises endpoint singularities
from multi-dimensional parameter integrals and can serve to calculate integrals
occurring in higher order perturbative calculations numerically. We focus on
the new features and on frequently asked questions about the usage of the
program.Comment: 11 pages, to appear in the proceedings of the HiggsTools Final
Meeting, IPPP, University of Durham, UK, September 201
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