82 research outputs found
Effect of the Coulomb repulsion on the {\it ac} transport through a quantum dot
We calculate in a linear response the admittance of a quantum dot out of
equilibrium. The interaction between two electrons with opposite spins
simultaneously residing on the resonant level is modeled by an Anderson
Hamiltonian. The electron correlations lead to the appearence of a new feature
in the frequency dependence of the conductance. For certain parameter values
there are two crossover frequencies between a capacitive and an inductive
behavior of the imaginary part of the admittance. The experimental implications
of the obtained results are briefly discussed.Comment: 13 pages, REVTEX 3.0, 2 .ps figures from [email protected],
NUB-308
Transport in Coupled Quantum Dots: Kondo Effect Versus Anti-Ferromagnetic Correlation
The interplay between the Kondo effect and the inter-dot magnetic interaction
in a coupled-dot system is studied. An exact result for the transport
properties at zero temperature is obtained by diagonalizing a cluster, composed
by the double-dot and its vicinity, which is connected to leads. It is shown
that the system goes continuously from the Kondo regime to an
anti-ferromagnetic state as the inter-dot interaction is increased. The
conductance, the charge at the dots and the spin-spin correlation are obtained
as a function of the gate potential.Comment: 4 pages, 3 postscript figures. Submitted to PR
Measurement of the ratio of the leptonic widths for the meson
The ratio of the electron and muon widths of the meson has been
measured using direct decays in the KEDR experiment at the VEPP-4M
electron-positron collider. The result
$\Gamma_{ee}(J/\psi)/\Gamma_{\mu\mu}(J/\psi)=1.0022\pm0.0044\pm0.0048\
(0.65\%)J/\psi$ lepton width
determination with up to 1% accuracy.Comment: 5 pages, 6 figures, 2 table
PGE reefs of the West-Pana layered intrusion, Kola Region, Russia: plagioclase composition as an indicator of the economic potential
The PARETO RATING Software System for the Paretoapproximation Quality Assessment in Multi-criteria Optimization Problem
We consider the task to assess the quality of Pareto set (front) numerical approximation in a multi-criteria optimization (MOC) problem. We mean that Pareto-approximation is obtained by means of this or that population e.g. genetic algorithm.Eventually, the purpose of work is a comparative assessment of the efficiency of population algorithms of Pareto-approximation. The great number of characteristics (indicators) of the Pareto-approximation quality is developed. Therefore an assessment problem of the Paretoapproximation quality is also considered as multi-criteria (multi-indicator). There are a number of well-known software systems to solve an assessment problem of the Pareto-approximation quality in different degree. Common drawback of these systems is a lack of both the WEB INTERFACE and the support of a multi-indicator assessment of Pareto-approximation quality (though there is a support to calculate the values of a large number of these indicators). The PARETO RATING software system is urged to eliminate the specified shortcomings of known systems. As population algorithms of Pareto-approximation are, as a rule, stochastic, we consider statistical methods to assess the quality of two and more Pareto-approximations (and thereby the estimates of algorithms used to obtain these approximations as well) as follows: methods based on the ranging of the specified approximations; methods based on the quality indicators; methods based on the so-called empirical functions of approachability. We give formal statement of the MOC-problem and general scheme of the population algorithms of its solution, present reviews of known indicators of Pareto-approximation quality and statistical methods for assessment of Pareto-approximation quality. We describe the system architecture and main features of its software implementation and illustrate efficiency of made algorithmic and software solutions.</p
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