Singular values and Schmidt pairs of composition operators on the Hardy space (Q1771392)

The main result of the present paper solves the functional equation \[ G(z)f(\varphi(z))=\lambda f(z), \] where \(G\) is a given bounded analytic function in the unit disk \(D\) and \(\varphi\) is a given analytic self-map of \(D\). The unknowns of the equation are \(f\), which is to be analytic in \(D\), and \(\lambda\), which is to be a complex number. As a consequence, the singular values of the compact composition operator \(C_\varphi\) on the classical Hardy space \(H^2\) are computed, where \(\varphi(z)=az+b\) with \(| a| +| b| <1\). The corresponding problem for weighted Bergman spaces is discussed as well.