Shigenori Matsumoto

Stochastic resonance with group chase and escape

We describe a simple model developed under the new idea of one group chasing another called, “group chase and escape”. We will demonstrate that even a simple model can exhibit rather rich and complex behavior. In particular, we show that the appropriate level of fluctuation in each step of the process for chase and escape can minimize the time taken for the entire catch.

A glimpse of fluid turbulence from the molecular scale

Large-scale molecular dynamics (MD) simulations of freely decaying turbulence in three-dimensional space are reported. Fluid components are defined from the microscopic states by eliminating thermal components from the coarse-grained fields. The energy spectrum of the fluid components is observed to scale reasonably well according to Kolmogorov scaling determined from the energy dissipation rate and the viscosity of the fluid, even though the Kolmogorov length is of the order of the molecular scale.

Dynamical aspect of group chase and escape

Recently, a new concept is proposed for chasing and evading in crowds, called “group chase and escape” through a simple model. In this model, two kinds of players, chasers and escapees, play tag on a two‐dimensional square lattice. Each chaser approaches its nearest escapee. On the other hand, each escapee steps away from its nearest chaser. Although there are no communications within each group, players appear to cooperate among themselves to chase or escape. We found relation between this cooperative behavior and group formations depend on the density of chasers and targets.

Chases and Escapes: From Singles to Groups

“Chases and escapes” is a traditional mathematical problem. The act of balancing a stick on human fingertips represents an experimental paradigm of typical “one-to-one” chase and escape. Recently, we have proposed a simple model where we extend the chaser and escape to a case a group of particles chasing another group, called “group chase and escape.” This extension connects the traditional problem with current interests on collective motions of animals, insects, vehicles, etc. In this chapter, we present our basic model and its rather complex behavior. In the model, each chaser approaches its nearest escapee, while each escapee steps away from its nearest chaser. Although there are no communications within each group, simulations show segregations of chasers and targets. Two order parameters are introduced to characterize the chasing and escaping in group. Further developments are reviewed to extend our basic model.

Molecular dynamics simulation of ribosome jam

Abstract We propose a coarse-grained molecular dynamics model of ribosome molecules to study the dependence of translation process on environmental parameters. We found the model exhibits traffic jam property, which is consistent with an ASEP model. We estimated the influence of the temperature and concentration of molecules on the hopping probability used in the ASEP model. Our model can also treat environmental effects on the translation process that cannot be explained by such cellular automaton models.