Yasumasa Nishiura

I am interested in collision dynamics in dissipative systems and behaviors of traveling spots in heterogeneous media. In what follows I will describe it very briefly.
Spatially localized dissipative structures are ubiquitous such as vortex, chemical blob, discharge patterns, granular patterns, and binary convective motion. When they are moving, it is
unavoidable to observe various types of collisions. One of the main questions for the collision dynamics is that how we can describe the large deformation of each localized object at collision and predict its output. The strong collision usually causes topological changes such as merging into one body or splitting into several parts as well as annihilation. It is in general quite difficult to trace the details of the deformation unless it is a very weak interaction. We need a change in our way of thinking to solve this issue. So far we may stick too much to the deformation of each localized pattern and become shrouded in mystery. We try to characterize the hidden mechanism behind the deformation process. It may be instructive to think about the following metaphor: the droplet falling down the landscape with valleys and ridges. The motion of droplets on a rugged landscape is rather complicated; two droplets merge or split at the saddle points and they may sink into the underground, i.e., annihilation. On the other hand, the profile of the landscape remains unchanged and in fact it controls the behaviors of droplets. It may be worth to describe the landscape itself rather than complex deformation, namely to find where is a ridge or a valley, and how they are combined to form a whole landscape. Such a change of viewpoint has been proposed recently claiming that the network of unstable patterns relevant to the collision process constitutes the backbone structure of the deformation process, namely the deformation is guided by the connecting orbits among the nodes of the network. Each node is typically an unstable ordered pattern such as steady state or time-periodic solution. This view point is quite useful and can be applicable to various problems, especially, the dynamics in heterogeneous media is one of the interesting applications. External environments can be regarded as a heterogeneity for moving objects so that questions of adaptability in biological systems may fall in this category when they are reformulated in an appropriate way. See the recent works for more details.

I am serving as an editor of the following journals:
1.Physica D
2.European J.of Appl.Math.(Jan.1, 2008 - Dec.30, 2011)
3.Chaos
4.SIADS (SIAM Journal on Applied Dynamical Systems)
5.Multiscale Modeling and Simulation: A SIAM Interdisciplinary Journal

Also I worked as the program director of JST Math Program from 2007 to 2016: http://www.math.jst.go.jp/en/index.html