For a left-exact functor F on an abelian category with enough injectives, the right-derived functors R^n F(A) = H^n(F(I•)) for injective resolution A → I•. Right-exact + projective resolutions gives left-derived functors. Tor and Ext are…
For a left-exact functor F on an abelian category with enough injectives, the right-derived functors R^n F(A) = H^n(F(I•)) for injective resolution A → I•. Right-exact + projective resolutions gives left-derived functors. Tor and Ext are…