Equations for Chow and Hilbert quotients

Abstract

We give explicit equations for the Chow and Hilbert quotients of a projective scheme X by the action of an algebraic torus T in an auxiliary toric variety. As a consequence we provide geometric invariant theory descriptions of these canonical quotients, and obtain other GIT quotients of X by variation of GIT quotient. We apply these results to find equations for the moduli space M0,n of stable genus-zero n-pointed curves as a subvariety of a smooth toric variety defined via tropical methods. ©2010 by Mathematical Sciences Publishers.