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Squarefree monomial ideals with maximal depth

Ahad Rahimi (2020)

Czechoslovak Mathematical Journal

Let ( R , 𝔪 ) be a Noetherian local ring and M a finitely generated R -module. We say M has maximal depth if there is an associated prime 𝔭 of M such that depth M = dim R / 𝔭 . In this paper we study squarefree monomial ideals which have maximal depth. Edge ideals of cycle graphs, transversal polymatroidal ideals and high powers of connected bipartite graphs with this property are classified.

Stable short exact sequences and the maximal exact structure of an additive category

Wolfgang Rump (2015)

Fundamenta Mathematicae

It was recently proved that every additive category has a unique maximal exact structure, while it remained open whether the distinguished short exact sequences of this canonical exact structure coincide with the stable short exact sequences. The question is answered by a counterexample which shows that none of the steps to construct the maximal exact structure can be dropped.

Standard monomials for q-uniform families and a conjecture of Babai and Frankl

Gábor Hegedűs, Lajos Rónyai (2003)

Open Mathematics

Let n, k, α be integers, n, α>0, p be a prime and q=p α. Consider the complete q-uniform family k , q = K n : K k ( m o d q ) We study certain inclusion matrices attached to F(k,q) over the field 𝔽 p . We show that if l≤q−1 and 2l≤n then r a n k 𝔽 p I ( ( k , q ) , n ) n This extends a theorem of Frankl [7] obtained for the case α=1. In the proof we use arguments involving Gröbner bases, standard monomials and reduction. As an application, we solve a problem of Babai and Frankl related to the size of some L-intersecting families modulo q.

Stanley decompositions and polarization

Sarfraz Ahmad (2011)

Czechoslovak Mathematical Journal

We define nice partitions of the multicomplex associated with a Stanley ideal. As the main result we show that if the monomial ideal I is a CM Stanley ideal, then I p is a Stanley ideal as well, where I p is the polarization of I .

Stanley depth of monomial ideals with small number of generators

Mircea Cimpoeaş (2009)

Open Mathematics

For a monomial ideal I ⊂ S = K[x 1...,x n], we show that sdepth(S/I) ≥ n − g(I), where g(I) is the number of the minimal monomial generators of I. If I =νI′, where ν ∈ S is a monomial, then we see that sdepth(S/I) = sdepth(S/I′). We prove that if I is a monomial ideal I ⊂ S minimally generated by three monomials, then I and S/I satisfy the Stanley conjecture. Given a saturated monomial ideal I ⊂ K[x 1,x 2,x 3] we show that sdepth(I) = 2. As a consequence, sdepth(I) ≥ sdepth(K[x 1,x 2,x 3]//I) +1...

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