Consider a map . We say that a vector field projects on if they are -related vector fields. We will say that is projectable if it projects to some vector field on . See @saunders1989geometry page 67.
Given an involutive distribution (i.e., a foliation) on a manifold , a vector field is said to be projectable with respect to (in the sense of @paola.frobenius) if for every we have
They are also known as foliate vector fields, basic vector fields, base-like vector fields, foliated vector fields,... (see [Molino 1988] page 35)
In particular, it may happen that , and the requirement becomes
We can say that is a -projectable vector field.
But, what is happening when we reduce an ODE with a symmetry? I.e., when we have a vector field associated to an ODE and
The point here is that the vector field is not -projectable, but the distribution is. The projection converts the vector field in a nonlocal vector field!?
But we would have had the same phenomenon if , i.e., if were a cinf-symmetry.
This open the door to: a distribution is -projectable if is involutive, that is, is a cinf-symmetry of distribution.