English

Stanley-Reisner rings, sheaves, and Poincare-Verdier duality

Commutative Algebra 2007-05-23 v2

Abstract

Recently, I defined a squarefree module over a polynomial ring S=k[x1,>...,xn]S = k[x_1, >..., x_n] generalizing the Stanley-Reisner ring k[Δ]=S/IΔk[\Delta] = S/I_\Delta of a simplicial complex Δ21,...,n\Delta \subset 2^{1, ..., n}. In this paper, from a squarefree module MM, we construct the kk-sheaf M+M^+ on an (n1)(n-1) simplex BB which is the geometric realization of 21,...,n2^{1, ..., n}. For example, k[Δ]+k[\Delta]^+ is (the direct image to BB of) the constant sheaf on the geometric realization ΔB|\Delta| \subset B. We have Hi(B,M+)=[Hmi+1(M)]0H^i(B, M^+) = [H^{i+1}_m(M)]_0 for all i>0i > 0. The Poincare-Verdier duality for sheaves M+M^+ on BB corresponds to the local duality for squarefree modules over SS. For example, if Δ|\Delta| is a manifold, then k[Δ]k[\Delta] is a Buchsbaum ring whose canonical module is a squarefree module giving the orientation sheaf of Δ|\Delta| with the coefficients in kk.

Keywords

Cite

@article{arxiv.math/0301030,
  title  = {Stanley-Reisner rings, sheaves, and Poincare-Verdier duality},
  author = {Kohji Yanagawa},
  journal= {arXiv preprint arXiv:math/0301030},
  year   = {2007}
}

Comments

15 pages. In the newest version, I have modified some minor places. To appear in Mathematical Research Letters