3,583 research outputs found

    Calibration of the Particle Density in Cellular-Automaton Models for Traffic Flow

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    We introduce density dependence of the cell size in cellular-automaton models for traffic flow, which allows a more precise correspondence between real-world phenomena and what observed in simulation. Also, we give an explicit calibration of the particle density particularly for the asymmetric simple exclusion process with some update rules. We thus find that the present method is valid in that it reproduces a realistic flow-density diagram.Comment: 2 pages, 2 figure

    Exact solution and asymptotic behaviour of the asymmetric simple exclusion process on a ring

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    In this paper, we study an exact solution of the asymmetric simple exclusion process on a periodic lattice of finite sites with two typical updates, i.e., random and parallel. Then, we find that the explicit formulas for the partition function and the average velocity are expressed by the Gauss hypergeometric function. In order to obtain these results, we effectively exploit the recursion formula for the partition function for the zero-range process. The zero-range process corresponds to the asymmetric simple exclusion process if one chooses the relevant hop rates of particles, and the recursion gives the partition function, in principle, for any finite system size. Moreover, we reveal the asymptotic behaviour of the average velocity in the thermodynamic limit, expanding the formula as a series in system size.Comment: 10 page

    Depth profile photoemission study of thermally diffused Mn/GaAs (001) interfaces

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    We have performed a depth profile study of thermally diffused Mn/GaAs (001) interfaces using photoemission spectroscopy combined with Ar+^+-ion sputtering. We found that Mn ion was thermally diffused into the deep region of the GaAs substrate and completely reacted with GaAs. In the deep region, the Mn 2pp core-level and Mn 3dd valence-band spectra of the Mn/GaAs (001) sample heated to 600 ^{\circ}C were similar to those of Ga1x_{1-x}Mnx_xAs, zinc-blende-type MnAs dots, and/or interstitial Mn in tetrahedrally coordinated by As atoms, suggesting that the Mn 3dd states were essentially localized but were hybridized with the electronic states of the host GaAs. Ferromagnetism was observed in the dilute Mn phase.Comment: 5 pages, 4 figure

    Measuring errors in single qubit rotations by pulsed electron paramagnetic resonance

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    The ability to measure and reduce systematic errors in single-qubit logic gates is crucial when evaluating quantum computing implementations. We describe pulsed electron paramagnetic resonance (EPR) sequences that can be used to measure precisely even small systematic errors in rotations of electron-spin-based qubits. Using these sequences we obtain values for errors in rotation angle and axis for single-qubit rotations using a commercial EPR spectrometer. We conclude that errors in qubit operations by pulsed EPR are not limiting factors in the implementation of electron-spin based quantum computers

    Band Calculations for Ce Compounds with AuCu3_{3}-type Crystal Structure on the basis of Dynamical Mean Field Theory I. CePd3_{3} and CeRh3_{3}

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    Band calculations for Ce compounds with the AuCu3_{3}-type crystal structure were carried out on the basis of dynamical mean field theory (DMFT). The auxiliary impurity problem was solved by a method named NCAf2f^{2}vc (noncrossing approximation including the f2f^{2} state as a vertex correction). The calculations take into account the crystal-field splitting, the spin-orbit interaction, and the correct exchange process of the f1f0,f2f^{1} \rightarrow f^{0},f^{2} virtual excitation. These are necessary features in the quantitative band theory for Ce compounds and in the calculation of their excitation spectra. The results of applying the calculation to CePd3_{3} and CeRh3_{3} are presented as the first in a series of papers. The experimental results of the photoemission spectrum (PES), the inverse PES, the angle-resolved PES, and the magnetic excitation spectra were reasonably reproduced by the first-principles DMFT band calculation. At low temperatures, the Fermi surface (FS) structure of CePd3_{3} is similar to that of the band obtained by the local density approximation. It gradually changes into a form that is similar to the FS of LaPd3_{3} as the temperature increases, since the 4f4f band shifts to the high-energy side and the lifetime broadening becomes large.}Comment: 12 pasges, 13 figure
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