A smörgåsbord of scalar-flat Kähler ALE surfaces

Abstract: There are many known examples of scalar-flat K\"ahler ALE surfaces, all of which have group at infinity either cyclic or contained in ${\rm{SU}}(2)$. The main result in this paper shows that for any non-cyclic finite subgroup $\Gamma \subset {\rm{U}}(2)$ containing no complex reflections, there exist scalar-flat K\"ahler ALE metrics on the minimal resolution of $\mathbb{C}^2 / \Gamma$, for which $\Gamma$ occurs as the group at infinity. Furthermore, we show that these metrics admit a holomorphic isometric circle action. It is also shown that there exist scalar-flat K\"ahler ALE metrics with respect to some small deformations of complex structure of the minimal resolution. Lastly, we show the existence of extremal K\"ahler metrics admitting holomorphic isometric circle actions in certain K\"ahler classes on the complex analytic compactifications of the minimal resolutions.