Global relation for the half-line free Schrodinger equation (source code)

= Global relation for the half-line free Schrodinger equation

For $u_t=iu_{xx}$ on $x>0$, the half-line Fourier transform satisfies
$$
\widehat u_t+ik^2\widehat u=kh(t)-iu_x(0,t).
$$
Subtracting the relation at $-k$ cancels the unknown Neumann datum. Fourier inversion of the resulting odd combination gives the solution in terms of the initial transform and the prescribed Dirichlet datum, with boundary kernel $G(k,t)=kh(t)$.