English

Local cohomology modules of invariant rings

Commutative Algebra 2019-02-20 v2

Abstract

Let KK be a field and let RR be a regular domain containing KK. Let GG be a finite subgroup of the group of automorphisms of RR. We assume that G|G| is invertible in KK. Let RGR^G be the ring of invariants of GG. Let II be an ideal in RGR^G. Fix i0i \geq 0. If RGR^G is Gorenstein then, \begin{enumerate} \item injdimRGHIi(RG)dim Supp HIi(RG).injdim_{R^G} H^i_I(R^G) \leq \dim \ Supp \ H^i_I(R^G). \item Hmj(HIi(RG))H^j_{\mathfrak{m}}(H^i_I(R^G)) is injective, where m\mathfrak{m} is any maximal ideal of RGR^G. \item μj(P,HIi(RG))=μj(P,HIRi(R))\mu_j(P, H^i_I(R^G)) = \mu_j(P^\prime, H^i_{IR}(R)) where PP^\prime is any prime in RR lying above PP. \end{enumerate} We also prove that if PP is a prime ideal in RGR^G with RPGR^G_P \textit{not Gorenstein} then either the bass numbers μj(P,HIi(RG))\mu_j(P, H^i_I(R^G)) is zero for all jj or there exists cc such that μj(P,HIi(RG))=0\mu_j(P, H^i_I(R^G)) = 0 for j<cj < c and μj(P,HIi(RG))>0\mu_j(P, H^i_I(R^G)) > 0 for all jcj \geq c.

Keywords

Cite

@article{arxiv.1310.4626,
  title  = {Local cohomology modules of invariant rings},
  author = {Tony J. Puthenpurakal},
  journal= {arXiv preprint arXiv:1310.4626},
  year   = {2019}
}

Comments

Some of the results in the previous version was already known by work of N\'{u}\~{n}ez-Betancourt. Those results have been removed in this version. Also some new results are added