Beurling–Lax theorem

In mathematics, the Beurling–Lax theorem is a theorem due to Beurling (1949) and Lax (1959) which characterizes the shift-invariant subspaces of the Hardy space H^2(\mathbb{D},\mathbb{C}). It states that each such space is of the form

 \theta H^2(\mathbb{D},\mathbb{C}),

for some inner function \theta.

See also

References