Group chase and escape

We describe here a new concept of one group chasing another, called 'group chase and escape', by presenting a simple model. We will show that even a simple model can demonstrate rather rich and complex behavior. In particular, there are cases where an optimal number of chasers exists for a given number of escapees (or targets) to minimize the cost of catching all targets. We have also found an indication of self-organized spatial structures formed by both groups.