“…The second part of the question above, therefore, is where the real question lies. The above question has been discussed in different contexts, including: slope stability, Gieseker stability and Bridgeland stabiliy on Abelian surfaces [21,33,9,37,38,22], slope stability and Gieseker stability on K3 surfaces [3,2,16,12], twisted stability on Abelian and K3 surfaces [35,36,25], rank-one torsion-free sheaves on elliptic surfaces [37,38,8], rank-one torsionfree sheaves on elliptic threefolds [11], torsion sheaves on elliptic threefolds [14], torsion sheaves on K3-surface fibrations [1], and from the point of view of Postnikov stability [15], just to name a few. A comprehensive introduction to results of this type can be found in [4].…”