For a dynamical system x'=f(x), is there a name for a set of points y such that f(x+y)=f(x)?

1. I would like to find a commonly used name for dynamical systems x' = f(x) such that f(x+y) = f(x) (dynamics of the system is invariant subject to particular coordinate change, the function...

16 April 2015 3,471 4 View