Crepant Terminalisations and Orbifold Euler Numbers for SL(4) Singularities

Abstract

Let $X$ and $Y$ be two analytic canonical Gorenstein orbifolds. A resolution of singularities $Y\to X$ is called an Euler resolution if $Y$ and $X$ have the same orbifold Euler number. If $Y$ is only terminal rather than smooth, it is called an Euler terminalisation. It is proved that Euler terminalisations exist for toric varieties in any dimension, for 4-dimensional toroidal varieties, and for singularities $\C^4/G$ where $G$ belongs to certain classes of $\SL(4)$ subgroups. The method of proof is expected to be applicable to a sizeable number of finite $\SL(4)$ subgroups and to lead to a generalisation of the Dixon-Harvey-Vafa-Witten orbifold Euler number conjecture to dimension~4.