English

Dualizing complex of the incidence algebra of a finite regular cell complex

Rings and Algebras 2007-05-23 v3 Commutative Algebra Combinatorics

Abstract

Let Σ\Sigma be a finite regular cell complex with Σ\emptyset \in \Sigma, and regard it as a partially ordered set (poset) by inclusion. Let RR be the incidence algebra of the poset Σ\Sigma over a field kk. Corresponding to the Verdier duality for constructible sheaves on Σ\Sigma, we have a dualizing complex wDb(modRkR)w \in D^b(mod_{R \otimes_k R}) giving a duality functor from Db(modR)D^b(mod_R) to itself. ww satisfies the Auslander condition. Our duality is somewhat analogous to the Serre duality for projective schemes (\emptyset plays a similar role to that of "irrelevant ideals"). If Hi(w)0H^i(w) \ne 0 for exactly one ii, then the underlying topological space of Σ\Sigma is Cohen-Macaulay (in the sense of the Stanley-Reisner ring theory). The converse also holds when Σ\Sigma is a simplicial complex. RR is always a Koszul ring with R!RopR^! \cong R^op. The relation between the Koszul duality for RR and the Verdier duality is discussed. This result is a variant of a theorem of Vybornov. The Mobius function of the poset Σ^\hat{\Sigma} is also discussed.

Keywords

Cite

@article{arxiv.math/0407383,
  title  = {Dualizing complex of the incidence algebra of a finite regular cell complex},
  author = {Kohji Yanagawa},
  journal= {arXiv preprint arXiv:math/0407383},
  year   = {2007}
}

Comments

18 pages. The results are almost same. But the exposition has been totally revised emphasizing combinatorial aspects