The symplectic mapping class group of $\CC P^2 n{\bar{\CC P^2}}$ with $n\le 4$

Jun Li, Tian-Jun Li, Weiwei Wu

In this paper we prove that the Torelli part of the symplectomorphism groups of the $n$-point ($n\le 4$) blow-ups of the projective plane is trivial. Consequently, we determine th…