From points to complexes: a concept of unexpectedness for simplicial complexes

Fuente: arXiv
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Autor principal: Holleben, Thiago
Formato: Preprint
Publicado: 2025
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author Holleben, Thiago
author_facet Holleben, Thiago
contents In 2018, Cook, Harbourne, Migliore and Nagel introduced the concept of unexpected hypersurfaces, which connects the study of Lefschetz properties of artinian algebras defined by powers of linear forms, to a family of interpolation problems. In this paper, inspired by the theory of unexpected hypersurfaces, we introduce the concept of unexpected systems of parameters for squarefree monomial ideals. Similarly to the setting of points, we show that the existence of an unexpected system of parameters causes a certain algebra to fail the weak Lefschetz property. We then explore combinatorial interpretations of unexpected systems of parameters, and show that this notion is intrinsically related to the theory of balanced complexes. A consequence of our results is that the theory of Rees algebras turns out to be a powerful tool for studying the existence of systems of parameters satisfying special properties.
format Preprint
id arxiv_https___arxiv_org_abs_2510_10884
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle From points to complexes: a concept of unexpectedness for simplicial complexes
Holleben, Thiago
Commutative Algebra
Combinatorics
13E10, 13F55, 05E45, 05E40
In 2018, Cook, Harbourne, Migliore and Nagel introduced the concept of unexpected hypersurfaces, which connects the study of Lefschetz properties of artinian algebras defined by powers of linear forms, to a family of interpolation problems. In this paper, inspired by the theory of unexpected hypersurfaces, we introduce the concept of unexpected systems of parameters for squarefree monomial ideals. Similarly to the setting of points, we show that the existence of an unexpected system of parameters causes a certain algebra to fail the weak Lefschetz property. We then explore combinatorial interpretations of unexpected systems of parameters, and show that this notion is intrinsically related to the theory of balanced complexes. A consequence of our results is that the theory of Rees algebras turns out to be a powerful tool for studying the existence of systems of parameters satisfying special properties.
title From points to complexes: a concept of unexpectedness for simplicial complexes
topic Commutative Algebra
Combinatorics
13E10, 13F55, 05E45, 05E40
url https://arxiv.org/abs/2510.10884