Factorially graded rings and Cox rings

Abstract: Cox rings of normal prevarieties are factorially graded, i.e. homogeneous elements allow a unique decomposition into homogeneous factors. We study this property from an algebraic point of view and give a criterion which in a sense reduces it to factoriality. This will allow us to detect and construct Cox rings in a purely algebraic manner. [Copyright &y& Elsevier]