Invertible Sheaf - The Picard Group

The Picard Group

Quite generally, the isomorphism classes of invertible sheaves on X themselves form an abelian group under tensor product. This group generalises the ideal class group. In general it is written

with Pic the Picard functor. Since it also includes the theory of the Jacobian variety of an algebraic curve, the study of this functor is a major issue in algebraic geometry.

The direct construction of invertible sheaves by means of data on X leads to the concept of Cartier divisor.

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