Faltings' annihilator theorem

In abstract algebra (specifically commutative ring theory), Faltings' annihilator theorem states: given a finitely generated module M over a Noetherian commutative ring A and ideals I, J, the following are equivalent:[1]

  • depth M p + ht ( I + p ) / p n {\displaystyle \operatorname {depth} M_{\mathfrak {p}}+\operatorname {ht} (I+{\mathfrak {p}})/{\mathfrak {p}}\geq n} for any p Spec ( A ) V ( J ) {\displaystyle {\mathfrak {p}}\in \operatorname {Spec} (A)-V(J)} ,
  • there is an ideal b {\displaystyle {\mathfrak {b}}} in A such that b J {\displaystyle {\mathfrak {b}}\supset J} and b {\displaystyle {\mathfrak {b}}} annihilates the local cohomologies H I i ( M ) , 0 i n 1 {\displaystyle \operatorname {H} _{I}^{i}(M),0\leq i\leq n-1} ,

provided either A has a dualizing complex or is a quotient of a regular ring.

The theorem was first proved by Faltings in (Faltings 1981).

References

  1. ^ Takesi Kawasaki, On Faltings' Annihilator Theorem, Proceedings of the American Mathematical Society, Vol. 136, No. 4 (Apr., 2008), pp. 1205–1211. NB: since ht ( ( I + p ) / p ) = inf ( ht ( r / p ) r V ( p ) V ( I ) = V ( ( I + p ) / p ) } {\displaystyle \operatorname {ht} ((I+{\mathfrak {p}})/{\mathfrak {p}})=\operatorname {inf} (\operatorname {ht} ({\mathfrak {r}}/{\mathfrak {p}})\mid {\mathfrak {r}}\in V({\mathfrak {p}})\cap V(I)=V((I+{\mathfrak {p}})/{\mathfrak {p}})\}} , the statement here is the same as the one in the reference.
  • Faltings, Gerd (1981). "Der Endlichkeitssatz in der lokalen Kohomologie". Mathematische Annalen. 255: 45–56.


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