Left shift operator (source code)

= Left shift operator
{title2=$L(f_1,f_2,\ldots)=(f_2,f_3,\ldots)$}

On the <Hilbert space> $\ell^2(\mathbb N)$, the left shift deletes the first coordinate. It is the <adjoint operator> of the <unilateral shift operator> $S$. The identities $LS=I$ and $SLf=f-f_1e_1$ show that it is also the <Moore–Penrose inverse of an operator> for $S$; both maps have <operator norm> one.