A general formula for the index of depth stability of edge ideals
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arXiv
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| Format: | Preprint |
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2023
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| _version_ | 1866914788030808064 |
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| author | Lam, Ha Minh Trung, Ngo Viet Trung, Tran Nam |
| author_facet | Lam, Ha Minh Trung, Ngo Viet Trung, Tran Nam |
| contents | By a classical result of Brodmann, the function $\operatorname{depth} R/I^t$ is asymptotically a constant, i.e. there is a number $s$ such that $\operatorname{depth} R/I^t = \operatorname{depth} R/I^s$ for $t > s$. One calls the smallest number $s$ with this property the index of depth stability of $I$ and denotes it by $\operatorname{dstab}(I)$. This invariant remains mysterious til now. The main result of this paper gives an explicit formula for $\operatorname{dstab}(I)$ when $I$ is an arbitrary ideal generated by squarefree monomials of degree 2. That is the first general case where one can characterize $\operatorname{dstab}(I)$ explicitly. The formula expresses $\operatorname{dstab}(I)$ in terms of the associated graph. The proof involves new techniques which relate different topics such as simplicial complexes, systems of linear inequalities, graph parallelizations, and ear decompositions. It provides an effective method for the study of powers of edge ideals. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2308_15021 |
| institution | arXiv |
| publishDate | 2023 |
| record_format | arxiv |
| spellingShingle | A general formula for the index of depth stability of edge ideals Lam, Ha Minh Trung, Ngo Viet Trung, Tran Nam Commutative Algebra Combinatorics 13C05, 13C15 (Primary) 05C70, 05E40 (Secondary) By a classical result of Brodmann, the function $\operatorname{depth} R/I^t$ is asymptotically a constant, i.e. there is a number $s$ such that $\operatorname{depth} R/I^t = \operatorname{depth} R/I^s$ for $t > s$. One calls the smallest number $s$ with this property the index of depth stability of $I$ and denotes it by $\operatorname{dstab}(I)$. This invariant remains mysterious til now. The main result of this paper gives an explicit formula for $\operatorname{dstab}(I)$ when $I$ is an arbitrary ideal generated by squarefree monomials of degree 2. That is the first general case where one can characterize $\operatorname{dstab}(I)$ explicitly. The formula expresses $\operatorname{dstab}(I)$ in terms of the associated graph. The proof involves new techniques which relate different topics such as simplicial complexes, systems of linear inequalities, graph parallelizations, and ear decompositions. It provides an effective method for the study of powers of edge ideals. |
| title | A general formula for the index of depth stability of edge ideals |
| topic | Commutative Algebra Combinatorics 13C05, 13C15 (Primary) 05C70, 05E40 (Secondary) |
| url | https://arxiv.org/abs/2308.15021 |