X //_L G:=\operatorname{Proj} \left( \bigoplus_{n \geqslant 0} H^0(X, L^{\otimes n})^G \right).
If X is affine and L=\mathcal O_X(\chi) for a character \chi: G \to \mathbb G_m, then the GIT-quotient may be considered as
- first taking an affine quotient \operatorname{Spec} (\mathbb k[X]^{G_\chi}) by G_\chi:=\operatorname{Ker}(\chi: G \to \mathbb G_m),
- then taking a quotient by \mathbb G_m=G / G_\chi via replacing \operatorname{Spec} to \operatorname{Proj} of non-negative gradings.
For the details on the construction see
Mukai An introduction to invariants and moduli, remark 6.14.
The first step is fairly stupid, but a proof that GIT-quotient is very general is given in
Mumford Geometric invariant theory, converse 1.13 of chapter 1.4.
From MO:253379.
Mukai An introduction to invariants and moduli, remark 6.14.
The first step is fairly stupid, but a proof that GIT-quotient is very general is given in
Mumford Geometric invariant theory, converse 1.13 of chapter 1.4.
From MO:253379.