arXiv subjects

Yup Kim

Publications and source records attributed to Yup Kim.

25 records · Page 2Linked to original sources

arXiv2005

Anomalous kinetics of attractive $A+B \to 0$ reactions

We investigate the kinetics of $A+B \to 0$ reaction with the local attractive interaction between opposite species in one spatial dimension. The attractive interaction leads to isotropic diffusions inside segregated single species domains, and accelerates the reactions of opposite species at the domain boundaries. At equal initial densities of $A$ and $B$, we analytically and numerically show that the density of particles ($ρ$), the size of domains ($\ell$), the distance between the closest neighbor of same species ($\ell_{AA}$), and the distance between adjacent opposite species ($\ell_{AB}$) scale in time as $ρ\sim t^{-1/3}$, $\ell_{AA} \sim t^{1/3}$, and $\ell \sim \ell_{AB} \sim t^{2/3}$ respectively. These dynamical exponents form a new universality class distinguished from the class of uniformly driven systems of hard-core particles.

cond-mat.stat-mech↗

arXiv2005

Coevolutionary dynamics on scale-free networks

We investigate Bak-Sneppen coevolution models on scale-free networks with various degree exponents $γ$ including random networks. For $γ>3$, the critical fitness value $f_c$ approaches to a nonzero finite value in the limit $N \to \infty$, whereas $f_c$ approaches to zero as $2<γ\le 3$. These results are explained by showing analytically $f_c(N) \simeq A/<(k+1)^2>_N$ on the networks with size $N$. The avalanche size distribution $P(s)$ shows the normal power-law behavior for $γ>3$. In contrast, $P(s)$ for $2 <γ\le 3$ has two power-law regimes. One is a short regime for small $s$ with a large exponent $τ_1$ and the other is a long regime for large $s$ with a small exponent $τ_2$ ($τ_1 > τ_2$). The origin of the two power-regimes is explained by the dynamics on an artificially-made star-linked network.

cond-mat.stat-mech↗

arXiv2003

Herd Behaviors in the Stock and Foreign Exchange Markets

The herd behaviors of returns for the won-dollar exchange rate and the KOSPI are analyzed in Korean financial markets. It is shown that the probability distribution $P(R)$ of price returns $R$ for three values of the herding parameter tends to a power-law behavior $P(R) \simeq R^{-β}$ with the exponents $ β=2.2$(the won-dollar exchange rate) and 2.4(the KOSPI). The financial crashes are found to occur at $h >2.33$ when the relative increase in the probability distribution of exteremely high price returns is observed. Especially, the distribution of normalized returns shows a crossover to a Gaussian distribution for the time step $Δt=252$. Our results will be also compared to the other well-known analyses.

cond-mat.stat-mech↗

arXiv2003

Herd Behavior of Returns in the Futures Exchange Market

The herd behavior of returns is investigated in Korean futures exchange market. It is obtained that the probability distribution of returns for three types of herding parameter scales as a power law $R^{-β}$ with the exponents $ β=3.6$(KTB203) and 2.9(KTB209) in two kinds of Korean treasury bond. For our case since the active state of transaction exists to decrease lesser than the herding parameter $h=2.33$, the crash regime appears to increase in the probability with high returns values. Especially, we find that it shows a crossover toward a Gaussian probability function near the time step $Δt=360$ from the distribution of normalized returns. Our result will be also compared with other well-known results.

cond-mat.stat-mech↗

arXiv2002

Fluctuations of self-flattening surfaces

We study the scaling properties of self-flattening surfaces under global suppression on surface fluctuations. Evolution of self-flattening surfaces is described by restricted solid-on-solid type monomer deposition-evaporation model with reduced deposition (evaporation) at the globally highest (lowest) site. We find numerically that equilibrium surface fluctuations are anomalous with roughness exponent $α\simeq 1/3$ and dynamic exponent $z_W \simeq 3/2$ in one dimension (1D) and $α=0 (\log)$ and $z_W \simeq 5/2$ in 2D. Stationary roughness can be understood analytically by relating our model to the static self-attracting random walk model and the dissociative dimer type deposition-evaporation model. In case of nonequilibrium growing/eroding surfaces, self-flattening dynamics turns out to be irrelevant and the normal Kardar-Parisi-Zhang universality is recovered in all dimensions.

cond-mat.stat-mech↗

arXiv2002

Dynamical surface structures in multi-particle-correlated surface growths

We investigate the scaling properties of the interface fluctuation width for the $Q$-mer and $Q$-particle-correlated deposition-evaporation models. These models are constrained with a global conservation law that the particle number at each height is conserved modulo $Q$. In equilibrium, the stationary roughness is anomalous but universal with roughness exponent $α=1/3$, while the early time evolution shows nonuniversal behavior with growth exponent $β$ varying with models and $Q$. Nonequilibrium surfaces display diverse growing/stationary behavior. The $Q$-mer model shows a faceted structure, while the $Q$-particle-correlated model a macroscopically grooved structure.

cond-mat.stat-mech↗

arXiv1996

Dynamical Renormalization Group Study of a Conserved Surface Growth with Anti-Diffusive and Nonlinear Currents

Based on dynamical renormalization group (RG) calculations to the one-loop order, the surface growth described by a nonlinear stochastic conserved growth equation, {\partial h \over \partial t} = \pm ν_2 \nabla^2 h + λ\nabla \cdot (\nabla h)^3 + η, is studied analytically. The universality class of the growth described by the above equation with +{ν_2} (diffusion) is shown to be the same as that described by the Edwards-Wilkinson (EW) equation (i.e. +ν_2 and λ=0). In contrast our RG recursion relations manifest that the growth described by the above equation with {-ν_2}(anti-diffusion) is an unstable growth and do not reproduce the recent results from a numerical simulation by J. M. Kim [Phys. Rev. E 52, 6267 (1995)].

cond-mat↗