Composition operators between Toeplitz kernels

Abstract: Recently, we proved that the image of a Toeplitz kernel of dimension $>1$ under composition by an inner function is nearly $S^*$-invariant if and only if the inner function is an automorphism. In this paper, we build on this work and describe the minimal Toeplitz kernel containing the image of a Toeplitz kernel under a composition operator with an inner symbol. Furthermore, this work is extended to the minimal Toeplitz kernel containing the image of a Toeplitz kernel under a weighted composition operator. In particular, the corresponding cases for minimal model spaces are also formulated, generalizing known work on the action of composition operators on model spaces. Finally, the equivalences between Toeplitz kernels are used to formulate the specific maximal vectors for several Toeplitz kernels with symbols expressed in terms of composition operators and inner functions.