Published online by Cambridge University Press: 11 June 2020
Given a ${\mathcal{C}}^{\infty }$ expanding map
$T$ of the circle, we construct a Hilbert space
${\mathcal{H}}$ of smooth functions on which the transfer operator
${\mathcal{L}}$ associated to
$T$ acts as a compact operator. This result is made quantitative (in terms of singular values of the operator
${\mathcal{L}}$ acting on
${\mathcal{H}}$) using the language of Denjoy–Carleman classes. Moreover, the nuclear power decomposition of Baladi and Tsujii can be performed on the space
${\mathcal{H}}$, providing a bound on the growth of the dynamical determinant associated to
${\mathcal{L}}$.