On derived categories of K3 surfaces, symplectic automorphisms and the Conway group

In this note we interpret a recent result of Gaberdiel, Hohenegger and Volpato in terms of derived equivalences of K3 surfaces. We prove that there is a natural bijection between subgroups of the Conway group Co_1 with invariant lattice of rank at least four and groups of symplectic derived equivalences of D(Coh(X)) of projective K3 surfaces fixing a stability condition.