Friday, 28 October 2011

ag.algebraic geometry - Why is Proj of any graded ring isomorphic to Proj of a graded ring generated in degree one?

I have seen it stated that Proj of any graded ring $A$, finitely generated as an $A_0$-algebra, is isomorphic to Proj of a graded ring $B$ such that $B_0 = A_0$ and $B$ is generated as a $B_0$-algebra by $B_1$.



Could someone either supply a reference for or a sketch a proof of this statement?



Note: An obvious approach to this question is to make $B$ a Veronese subring of $A$. However, when I try this approach, I end up getting a terrible combinatorics problem that I do not know how to approach.

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