Some Properties of Products of Linear Fractional Composition Operators on Weighted Dirichlet Spaces

Abstract

We study the Schatten class membership and essential norms of the operators $C_φC_ψ^*$ and $C_ψ^*C_φ$, where $C_φ$ and $C_ψ$ are composition operators with nonconstant linear fractional symbols, acting on weighted Dirichlet spaces $\mathcal{D}_α$ with $α>-1$. We obtain complete characterizations of their Schatten class membership in terms of the boundary behavior of $φ$ and $ψ$. In particular, the corresponding geometric conditions are independent of the Schatten exponent, and each product belongs to every Schatten class whenever its boundary condition is satisfied. We also investigate the essential norms of these products. For $α=0$ and $α>0$, we obtain exact formulas in terms of boundary contact and the derivatives of the symbols, while for $-1<α<0$ we obtain two-sided estimates by reducing the problem to positive Toeplitz operators and local averages of generalized Nevanlinna counting functions.