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Eok Kyun Lee

Publications and source records attributed to Eok Kyun Lee.

4 recordsLinked to original sources

Numerical method for solving stochastic differential equations with dichotomous noise.

We propose a numerical method for solving stochastic differential equations with dichotomous Markov noise. The numerical scheme is formulated such that (i) the stochastic formula used follows the Stratonovich-Taylor form over the entire range of noise correlation times, including the Gaussian white noise limit; and (ii) the method is readily applicable to dynamical systems driven by arbitrary types of noise, provided there exists a way to describe the random increment of the stochastic process expressed in the Stratonovich-Taylor form. We further propose a simplified Taylor scheme that significantly reduces the computation time, while still satisfying the moment properties up to the required order. The accuracies and efficiencies of the proposed algorithms are validated by applying the schemes to two prototypical model systems that possess analytical solutions.

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Correlation between Kolmogorov-Sinai entropy and self-diffusion coefficient in simple fluids.

The relationship between the Kolmogorov-Sinai entropy, h(KS) and the self-diffusion coefficient D is studied for two classical simple fluid systems with purely repulsive potentials (one system with a Wayne-Chandler-Anderson potential and the other with a hard-sphere potential). Numerical simulation data for h(KS) and D, normalized by the average collision frequency nu and the diameter of the particle sigma as natural units of time and distance, reveal that, in the region spanning from normal liquid up to near solidification (0.50< or =rho< or =0.93), the Kolmogorov-Sinai entropy has a power law dependeney on the self-diffusion coefficient of the form h(KS)/nu proportional, variant (D/sigma(2)nu)(eta), in which eta is independent of density and temperature.

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Collapse of the metastable state in an attractive Bose-Einstein condensate.

The characteristic features of the collapse of the ground state in trapped one-component attractive Bose-Einstein condensates are studied by applying the catastrophe theory. From numerically obtained stable and unstable solutions of the Gross-Pitaevskii equation, we derive the catastrophe function defining the stability of the stationary points on the Gross-Pitaevskii energy functional. The bifurcation diagram and the universal scaling laws stemming from the catastrophe function show quantitative agreement with the numerical results.

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Characteristic features of symmetry breaking in two-component Bose-Einstein condensates.

We examine the stability properties of the ground state of two-component Bose-Einstein condensates as a function of the interspecies interactions. A stability criterion is identified from the curvature matrix of the Gross-Pitaevskii energy functional subject to the normalization conditions. By analyzing the stability signature, the characteristic features of the spontaneous spatial symmetry breaking are verified in various types of traps. The details of the differences between the continuous symmetry breaking and discrete symmetry breaking are discussed.

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