English

The $cl-core$ of an ideal

Commutative Algebra 2010-09-20 v3

Abstract

We expand the notion of core to clcl-core for Nakayama closures clcl. In the characteristic p>0p>0 setting, when clcl is the tight closure, denoted by *, we give some examples of ideals when the core and the *-core differ. We note that *-core(I)=(I)= core(I)(I), if II is an ideal in a one-dimensional domain with infinite residue field or if II is an ideal generated by a system of parameters in any Noetherian ring. More generally, we show the same result in a Cohen--Macaulay normal local domain with infinite perfect residue field, if the analytic spread, \ell, is equal to the *-spread and II is GG_{\ell} and weakly-(1)(\ell-1)-residually S2S_2. This last is dependent on our result that generalizes the notion of general minimal reductions to general minimal *-reductions. We also determine that the *-core of a tightly closed ideal in certain one-dimensional semigroup rings is tightly closed and therefore integrally closed.

Keywords

Cite

@article{arxiv.0810.3033,
  title  = {The $cl-core$ of an ideal},
  author = {Louiza Fouli and Janet Vassilev},
  journal= {arXiv preprint arXiv:0810.3033},
  year   = {2010}
}

Comments

Final version. Math. Proc. Camb. Phil. Soc 149 (2010) 247-262