“…Hence the only simple coherent sheaves on P 1 are the line bundles O P 1 (t ), t ∈ Z, and the sheaves O p , p ∈ P 1 . No pair of them, not even after a shift L 0 [−i ], L 1 [− j ] may be of this form: if p, q ∈ P 1 and p = q, then Ext i (O p , O q ) = 0 for all i , either Hom(R, L) = 0 or Ext 1 (L, R) = 0 for any line bundles L, R, Hom(O p , L) = 0 and dim Ext 1 (O p , L) = 1 for all p ∈ P 1 and any line bundle L. Since P 1 is a smooth curve, [10,Prop. 6.3] gives that every simple element of D b (P 1 ) is isomorphic to some F[−i ] with F a simple coherent sheaf on P 1 .…”