Published online by Cambridge University Press: 20 November 2018
Let ${{H}^{2}}\left( \Omega\right)$ be the Hardy space on a strictly pseudoconvex domain
$\Omega \,\subset \,{{\mathbb{C}}^{n}}$ , and let
$A\,\subset \,{{L}^{\infty }}\left( \partial \Omega\right)$ denote the subalgebra of all
${{L}^{\infty }}$ -functions
$f$ with compact Hankel operator
${{H}_{f}}$ . Given any closed subalgebra
$B\,\subset \,A$ containing
$C\left( \partial \Omega\right)$ , we describe the first Hochschild cohomology group of the corresponding Toeplitz algebra
$\mathcal{T}\left( B \right)\,\subset \,B\left( {{H}^{2}}\left( \Omega\right) \right)$ . In particular, we show that every derivation on
$\mathcal{T}\left( A \right)$ is inner. These results are new even for
$n\,=\,1$ , where it follows that every derivation on
$\mathcal{T}\left( {{H}^{\infty }}\,+\,C \right)$ is inner, while there are non-inner derivations on
$\mathcal{T}\left( {{H}^{\infty }}\,+\,C\left( \partial {{\mathbb{B}}_{n}} \right) \right)$ over the unit ball
${{\mathbb{B}}_{n}}$ in dimension
$n\,>\,1$ .