6,661 research outputs found
Perturbation approach to multifractal dimensions for certain critical random matrix ensembles
Fractal dimensions of eigenfunctions for various critical random matrix
ensembles are investigated in perturbation series in the regimes of strong and
weak multifractality. In both regimes we obtain expressions similar to those of
the critical banded random matrix ensemble extensively discussed in the
literature. For certain ensembles, the leading-order term for weak
multifractality can be calculated within standard perturbation theory. For
other models such a direct approach requires modifications which are briefly
discussed. Our analytical formulas are in good agreement with numerical
calculations.Comment: 28 pages, 7 figure
TEMPORAL PAYMENT ISSUES IN CONTINGENT VALUATION ANALYSIS
We analyze agent response to disparate payment schedules for protection of critical habitat units for the Seller sea lion in Alaska. The model allows for identification of implicit and explicit discount rates using information from a system of maximum likelihood equations. Testing is done using data for one, five, and fifteen year payment treatments.Research Methods/ Statistical Methods,
Consumer Preferences for Locally Made Specialty Food Products Across Northern New England
Does willingness to pay a premium for local specialty food products differ between consumers in Maine, New Hampshire, and Vermont? Two food categories are investigated: low-end (20) products. Premia estimates are compared across states and across base prices within states using dichotomous choice contingent valuation methods. Results suggest that the three states of northern New England have many similarities, including comparable price premia for the lower-priced good. However, there is some evidence that the premium for the higher-priced good is greater for the pooled Vermont and Maine treatment than for the New Hampshire treatment. Vermont and New Hampshire residents are willing to pay a higher premium for a 5 food item, while the evidence suggests that Maine residents are not.local specialty foods, willingness to pay, contingent valuation, Demand and Price Analysis, Food Consumption/Nutrition/Food Safety,
Coordinates, modes and maps for the density functional
Special bases of orthogonal polynomials are defined, that are suited to
expansions of density and potential perturbations under strict particle number
conservation. Particle-hole expansions of the density response to an arbitrary
perturbation by an external field can be inverted to generate a mapping between
density and potential. Information is obtained for derivatives of the
Hohenberg-Kohn functional in density space. A truncation of such an information
in subspaces spanned by a few modes is possible. Numerical examples illustrate
these algorithms.Comment: 15 pages, 9 figure
A note on the error analysis of classical Gram-Schmidt
An error analysis result is given for classical Gram--Schmidt factorization
of a full rank matrix into where is left orthogonal (has
orthonormal columns) and is upper triangular. The work presented here shows
that the computed satisfies \normal{R}=\normal{A}+E where is an
appropriately small backward error, but only if the diagonals of are
computed in a manner similar to Cholesky factorization of the normal equations
matrix.
A similar result is stated in [Giraud at al, Numer. Math.
101(1):87--100,2005]. However, for that result to hold, the diagonals of
must be computed in the manner recommended in this work.Comment: 12 pages This v2. v1 (from 2006) has not the biliographical reference
set (at all). This is the only modification between v1 and v2. If you want to
quote this paper, please quote the version published in Numerische Mathemati
Parallel scalability study of three dimensional additive Schwarz preconditioners in non-overlapping domain decomposition
In this paper we study the parallel scalability of variants of additive Schwarz preconditioners for three dimensional non-overlapping domain decomposition methods. To alleviate the
computational cost, both in terms of memory and floating-point complexity, we investigate
variants based on a sparse approximation or on mixed 32- and 64-bit calculation. The robustness of the preconditioners is illustrated on a set of linear systems arising from the finite
element discretization of elliptic PDEs through extensive parallel experiments on up to 1000
processors. Their efficiency from a numerical and parallel performance view point are studied
Delocalization transition for the Google matrix
We study the localization properties of eigenvectors of the Google matrix,
generated both from the World Wide Web and from the Albert-Barabasi model of
networks. We establish the emergence of a delocalization phase for the PageRank
vector when network parameters are changed. In the phase of localized PageRank,
a delocalization takes place in the complex plane of eigenvalues of the matrix,
leading to delocalized relaxation modes. We argue that the efficiency of
information retrieval by Google-type search is strongly affected in the phase
of delocalized PageRank.Comment: 4 pages, 5 figures. Research done at
http://www.quantware.ups-tlse.fr
Quantum computing of delocalization in small-world networks
We study a quantum small-world network with disorder and show that the system
exhibits a delocalization transition. A quantum algorithm is built up which
simulates the evolution operator of the model in a polynomial number of gates
for exponential number of vertices in the network. The total computational gain
is shown to depend on the parameters of the network and a larger than quadratic
speed-up can be reached.
We also investigate the robustness of the algorithm in presence of
imperfections.Comment: 4 pages, 5 figures, research done at
http://www.quantware.ups-tlse.fr
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