Tight closure/Generische Schranke/Parametersituation/Beispiel/en

Suppose that ${}n=d+1$ in the situation of Fakt. Then the generic elements ${}f_{1},\ldots ,f_{d+1}$ are parameters. In the polynomial ring ${}P=K[x_{0},x_{1},\ldots ,x_{d}]$ we have for parameters of degree ${}a_{1},\ldots ,a_{d+1}$ the inclusion

${}P_{\geq \sum _{i=0}^{d}a_{i}-d}\subseteq {\left(f_{1},\ldots ,f_{d+1}\right)}\,,$

because the graded Koszul resolution ends in ${}R(-\sum _{i=0}^{d}a_{i})$ and

$(H_{\mathfrak {m}}^{d+1}(P))_{k}=0{\text{ for }}k\geq -d.$

So the theorem implies for a graded ring ${}R$ finite over ${}P$ that ${}\subseteq (f_{1},\ldots ,f_{d+1})^{*}$ holds for generic elements. But by the graded Briançon-Skoda Theorem (see Fakt) this holds for parameters even without the generic assumption.