A Szeg\"o type theorem for truncated Toeplitz operators

Truncated Toeplitz operators are compressions of multiplication operators on $L^2$ to model spaces (that is, subspaces of $H^2$ which are invariant with respect to the backward shift). For this class of operators we prove certain Szeg"o type theorems concerning the asymptotics of their compressions to an increasing chain of finite dimensional model spaces.