From a short exact sequence of sheaves , the long exact sequence in sheaf cohomology gives the displayed isomorphism whenever . Repeating it along a locally free resolution shifts a fixed group to successively higher degrees. If all relevant kernel sheaves are quasi-coherent sheaves and there is a uniform vanishing bound for their sheaf cohomology, sufficiently many shifts force the original group to vanish. The cohomological dimension bound from an affine cover supplies such a bound for a closed subscheme of projective space.
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