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Published online by Cambridge University Press: 31 January 2018
Let $\unicode[STIX]{x1D711}$ be an analytic self-map of the unit disc. If
$\unicode[STIX]{x1D711}$ is analytic in a neighbourhood of the closed unit disc, we give a precise formula for the essential norm of the composition operator
$C_{\unicode[STIX]{x1D711}}$ on the weighted Dirichlet spaces
${\mathcal{D}}_{\unicode[STIX]{x1D6FC}}$ for
$\unicode[STIX]{x1D6FC}>0$. We also show that, for a univalent analytic self-map
$\unicode[STIX]{x1D711}$ of
$\mathbb{D}$, if
$\unicode[STIX]{x1D711}$ has an angular derivative at some point of
$\unicode[STIX]{x2202}\mathbb{D}$, then the essential norm of
$C_{\unicode[STIX]{x1D711}}$ on the Dirichlet space is equal to one.
This research is supported by NSFC grant no. 11671065. The third author is supported by the NSFC grant nos. 11271332 and 11431011.