A locally closed subscheme of a projective space . In other words, a quasi-projective scheme is an open subscheme of a projective scheme. A scheme over a field is quasi-projective if and only if there exists on an invertible ample sheaf. A generalization of the notion of a "quasi-projective scheme" is that of a quasi-projective morphism, that is, a morphism of schemes that is the composite of an open imbedding and a projective morphism. A scheme that is both quasi-projective and complete is projective.
|[a1]||R. Hartshorne, "Algebraic geometry" , Springer (1977) pp. 10; 103|
Quasi-projective scheme. Encyclopedia of Mathematics. URL: http://www.encyclopediaofmath.org/index.php?title=Quasi-projective_scheme&oldid=18339