Before revision: Controlled Invariant Subspace A subspace V is called controlled invariant , if for any x0 of V and such an input u, xu (t, x0 ) is in V, for all t nonnegative .
After revision: Controlled Invariant Subspace A subspace V is called controlled invariant , if for any x0 of V and such an input u, <math>x_u (t, x_0 ) is in V, for all nonnegative t .