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This paper investigates the shellability of $r$-independence complexes $\mathcal{I}_r(G)$, a generalization of classical independence complexes introduced by Paolini and Salvetti. For a graph $G$, a subset $A \subseteq V(G)$ is…

Combinatorics · Mathematics 2025-09-24 Arka Ghosh , S Selvaraja

We show that a large class of non-metric, non-symplectic affine holonomies can be realized, uniformly and without case by case considerations, by Weyl connections associated to the natural AHS-structures on certain generalized flag…

Differential Geometry · Mathematics 2008-11-18 Andreas Cap

Refining a basic result of Alexander, we show that two flag simplicial complexes are piecewise linearly homeomorphic if and only if they can be connected by a sequence of flag complexes, each obtained from the previous one by either an edge…

Combinatorics · Mathematics 2014-08-08 Frank H. Lutz , Eran Nevo

A flag complex can be defined as a simplicial complex whose simplices correspond to complete subgraphs of its 1-skeleton taken as a graph. In this article, by introducing the notion of s-dismantlability, we shall define the s-homotopy type…

Combinatorics · Mathematics 2019-06-04 Romain Boulet , Etienne Fieux , Bertrand Jouve

Let $H$ be a simple undirected graph and $G=\mathrm{L}(H)$ be its line graph. Assume that $\Delta(G)$ denotes the clique complex of $G$. We show that $\Delta(G)$ is sequentially Cohen-Macaulay if and only if it is shellable if and only if…

Commutative Algebra · Mathematics 2020-07-28 Ashkan Nikseresht

Ehrenborg, Govindaiah, Park, and Readdy recently introduced the van der Waerden complex, a pure simplicial complex whose facets correspond to arithmetic progressions. Using techniques from combinatorial commutative algebra, we classify when…

Combinatorics · Mathematics 2017-07-25 Becky Hooper , Adam Van Tuyl

We present a discrete Morse-theoretic method for proving that a regular CW complex is homeomorphic to a sphere. We use this method to define bisimplices, the cells of a class of regular CW complexes we call bisimplicial complexes. The…

Group Theory · Mathematics 2019-04-16 Nima Hoda

For a simplicial complex X on {1,2, ..., n} we define enriched homology and cohomology modules. They are graded modules over k[x_1, ..., x_n] whose ranks are equal to the dimensions of the reduced homology and cohomology groups. We…

Combinatorics · Mathematics 2011-12-14 Gunnar Floystad

We extend the definition of chordal from graphs to clutters. The resulting family generalizes both chordal graphs and matroids, and obeys many of the same algebraic and geometric properties. Specifically, the independence complex of a…

Combinatorics · Mathematics 2021-08-24 Russ Woodroofe

The matching complex of a simple graph $G$ is a simplicial complex consisting of the matchings on $G$. Jeli\'c Milutinovi\'c et al. studied the matching complexes of the polygonal line tilings, and they gave a lower bound for the…

Combinatorics · Mathematics 2022-06-17 Takahiro Matsushita

If a pure simplicial complex is partitionable, then its $h$-vector has a combinatorial interpretation in terms of any partitioning of the complex. Given a non-partitionable complex $\Delta$, we construct a complex $\Gamma \supseteq \Delta$…

Combinatorics · Mathematics 2021-11-01 Joseph Doolittle , Bennet Goeckner , Alexander Lazar

We study the independence complexes of families of well-covered circulant graphs discovered by Boros-Gurvich-Milani\v{c}, Brown-Hoshino, and Moussi. Because these graphs are well-covered, their independence complexes are pure simplicial…

Combinatorics · Mathematics 2015-05-13 Jonathan Earl , Kevin N. Vander Meulen , Adam Van Tuyl

We generalize the concept of a cycle from graphs to simplicial complexes. We show that a simplicial cycle is either a sequence of facets connected in the shape of a circle, or is a cone over such a structure. We show that a simplicial tree…

Commutative Algebra · Mathematics 2007-05-23 Massimo Caboara , Sara Faridi , Peter Selinger

We prove a reformulation of the multiplicity upper bound conjecture and use that reformulation to prove it for three-dimensional simplicial complexes and homology manifolds with many vertices. We provide necessary conditions for a…

Commutative Algebra · Mathematics 2008-02-12 Michael Goff

We illuminate the relation between the Bruhat order on the symmetric group and structure constants (Littlewood-Richardson coefficients) for the cohomology of the flag manifold in terms of its basis of Schubert classes. Equivalently, the…

alg-geom · Mathematics 2016-11-08 Nantel Bergeron , Frank Sottile

For a simplicial complex $\Delta$, we introduce a simplicial complex attached to $\Delta$, called the expansion of $\Delta$, which is a natural generalization of the notion of expansion in graph theory. We are interested in knowing how the…

Commutative Algebra · Mathematics 2016-01-05 Somayeh Moradi , Fahimeh Khosh-Ahang

We introduce the class of linearly shellable pure simplicial complexes. The characterizing property is the existence of a labeling of their vertices such that all linear extensions of the Bruhat order on the set of facets are shelling…

Combinatorics · Mathematics 2024-10-29 Paolo Sentinelli

We consider quotients of complete flag manifolds in Cn and Rn by an action of the symmetric group on n objects. We compute their cohomology with field coefficients of any characteristic. Specifically, we show that these topological spaces…

Algebraic Topology · Mathematics 2023-12-20 Lorenzo Guerra , Santanil Jana

In this article we introduce the notion of Polyhedral Kahler manifolds, even dimensional polyhedral manifolds with unitary holonomy. We concentrate on the 4-dimensional case, prove that such manifolds are smooth complex surfaces, and…

Differential Geometry · Mathematics 2016-08-04 Dmitri Panov

Scattered over the past few years have been several occurrences of simplicial complexes whose topological behavior characterize the Cohen-Macaulay property for quotients of polynomial rings by arbitrary (not necessarily squarefree) monomial…

Commutative Algebra · Mathematics 2008-09-10 Ezra Miller