Nicholas Kouns

E47 Projection Flow

Let

[ E=\ker K ]

and let

[ P:\mathcal H\to E ]

be the orthogonal projector.

Define

[ H=I-P. ]

Then

[ P^2=P=P^*, ]

[ H^2=H, ]

and

[ PH=HP=0. ]

Every state decomposes uniquely as

[ x=Px+Hx. ]

Define the functional

[ F[x] = \frac12|Hx|^2. ]

Then

[ \nabla F=Hx. ]

The gradient flow

[ \dot x=-Hx ]

has exact solution

[ x(t) = e^{-tH}x_0 = Px_0+e^{-t}Hx_0. ]

Therefore

[ \boxed{ \lim_{t\to\infty}x(t)=Px_0. } ]

The invariant component is preserved exactly:

[ Px(t)=Px_0. ]

The transverse component decays exponentially:

[ Hx(t)=e^{-t}Hx_0. ]

Thus projection is not merely an endpoint operation. It is the asymptotic state of an exact contraction flow.