Linear syzygies of Stanley-Reisner ideals

V Reiner, V Welker - Mathematica Scandinavica, 2001 - JSTOR
Mathematica Scandinavica, 2001JSTOR
We give an elementary description of the maps in the linear strand of the minimal free
resolution of a square-free monomial ideal, that is, the Stanley-Reisner ideal associated to a
simplicial complex△. The description is in terms of the homology of the canonical Alexander
dual complex△*. As applications we are able to• prove for monomial ideals and j= 1 a
conjecture of J. Herzog giving lower bounds on the number of i-syzygies in the linear strand
of jth-syzygy modules.• show that the maps in the linear strand can be written using only±1 …
We give an elementary description of the maps in the linear strand of the minimal free resolution of a square-free monomial ideal, that is, the Stanley-Reisner ideal associated to a simplicial complex △. The description is in terms of the homology of the canonical Alexander dual complex △*. As applications we are able to • prove for monomial ideals and j = 1 a conjecture of J. Herzog giving lower bounds on the number of i-syzygies in the linear strand of jth-syzygy modules. • show that the maps in the linear strand can be written using only ±1 coefficients if △* is a pseudomanifold, • exhibit an example where multigraded maps in the linear strand cannot be written using only ±1 coefficients. • compute the entire resolution explicity when △* is the complex of independent sets of a matroid.
JSTOR
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