English

Invariants of Linkage of modules

Commutative Algebra 2015-12-17 v1

Abstract

Let (A,m)(A,\mathfrak{m}) be a Gorenstein local ring and let M,NM, N be two Cohen-Macaulay \ AA-modules with MM linked to NN via a Gorenstein ideal q\mathfrak{q}. Let LL be another finitely generated AA-module. We show that ExtAi(L,M)=0Ext^i_A(L,M) = 0 for all i0i \gg 0 if and only if ToriA(L,N)=0Tor^A_i(L,N) = 0 for all i0i \gg 0. If DD is Cohen-Macaulay then we show that ExtAi(M,D)=0Ext^i_A(M, D) = 0 for all i0i \gg 0 if and only if ExtAi(D,N)=0Ext^i_A(D^\dagger, N) = 0 for all i0i \gg 0, where D=ExtAr(D,A)D^\dagger = Ext^r_A(D,A) and r=codim Dr = codim \ D. As a consequence we get that ExtAi(M,M)=0Ext^i_A(M, M) = 0 for all i0i \gg 0 if and only if ExtAi(N,N)=0Ext^i_A(N, N) = 0 for all i0i \gg 0. We also show that EndA(M)/rad EndA(M)(EndA(N)/rad EndA(N))opEnd_A(M)/rad \ End_A(M) \cong (End_A(N)/rad \ End_A(N))^{op}. We also give a negative answer to a question of Martsinkovsky and Strooker.

Keywords

Cite

@article{arxiv.1512.05105,
  title  = {Invariants of Linkage of modules},
  author = {Tony J. Puthenpurakal},
  journal= {arXiv preprint arXiv:1512.05105},
  year   = {2015}
}