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In an attempt to understanding the complexity of the independent set problem, Chv{\'a}tal defined t-perfect graphs. While a full characterization of this class is still at large, progress has been achieved for claw-free graphs [Bruhn and…

Discrete Mathematics · Computer Science 2022-11-08 Yixin Cao , Shenghua Wang

A total dominating set in a graph is a set of vertices such that every vertex of the graph has a neighbor in the set. We introduce and study graphs that admit non-negative real weights associated to their vertices such that a set of…

Combinatorics · Mathematics 2015-05-12 Nina Chiarelli , Martin Milanic

Given a family $\mathcal{H}$ of graphs, we say that a graph $G$ is $\mathcal{H}$-free if no induced subgraph of $G$ is isomorphic to a member of $\mathcal{H}$. Let $S_{t,t,t}$ be the graph obtained from $K_{1,3}$ by subdividing each edge…

Combinatorics · Mathematics 2025-02-10 Maria Chudnovsky , Julien Codsi , Daniel Lokshtanov , Martin Milanič , Varun Sivashankar

A dominating set of a graph $G$ is a set $S \subseteq V(G)$ such that every vertex in $V(G) \setminus S$ has a neighbor in $S$, where two vertices are neighbors if they are adjacent. A secure dominating set of $G$ is a dominating set $S$ of…

Combinatorics · Mathematics 2025-07-16 Uttam K. Gupta , Michael A. Henning , Paras Vinubhai Maniya , Dinabandhu Pradhan

We apply the homomorphism complex construction to partially ordered sets, introducing a new topological construction based on the set of maximal chains in a graded poset. Our primary objects of study are distributive lattices, with special…

Combinatorics · Mathematics 2018-12-27 Benjamin Braun , Wesley K. Hough

A set $S\subseteq V$ of a graph $G=(V,E)$ is a dominating set if each vertex has a neighbor in $S$ or belongs to $S$. Dominating Set is the problem of deciding, given a graph $G$ and an integer $k\geq 1$, if $G$ has a dominating set of size…

Combinatorics · Mathematics 2023-04-20 Valentin Bouquet , François Delbot , Christophe Picouleau , Stéphane Rovedakis

For a graph $G=(V,E)$, a subset $D$ of vertex set $V$, is a dominating set of $G$ if every vertex not in $D$ is adjacent to atleast one vertex of $D$. A dominating set $D$ of a graph $G$ with no isolated vertices is called a paired…

Discrete Mathematics · Computer Science 2021-12-13 Vikash Tripathi , Ton Kloks , Arti Pandey , Kaustav Paul , Hung-Lung Wang

Let $G$ be a simple, undirected, finite graph with vertex set $V(G)$ and edge set $E(G)$. A $k$-dimensional box is a Cartesian product of closed intervals $[a_1,b_1]\times [a_2,b_2]\times...\times [a_k,b_k]$. The {\it boxicity} of $G$,…

Combinatorics · Mathematics 2010-03-12 Abhijin Adiga , Diptendu Bhowmick , L. Sunil Chandran

Let $G=(V,E)$ be a graph with the vertex-set $V$ and the edge-set $E$. Let $N(v)$ denote the set of neighbors of the vertex $v$ of $G.$ The graph $G$ is called $ irreducible $ whenever for every $v,w \in V$ if $v \neq w$, then $N(v)\neq…

Group Theory · Mathematics 2020-09-24 S. Morteza Mirafzal

We introduce two partially ordered sets, $P^A_n$ and $P^B_n$, of the same cardinalities as the type-A and type-B noncrossing partition lattices. The ground sets of $P^A_n$ and $P^B_n$ are subsets of the symmetric and the hyperoctahedral…

Combinatorics · Mathematics 2007-05-23 Miklós Bóna , Rodica Simion

Nut graphs are graphs whose adjacency matrix is singular with one-dimensional null space spanned by a vector with no zero entries. In a recent paper, Ba\v{s}i\'c, Fowler and Pisanski proved that the automorphism group of a nut graph has…

Combinatorics · Mathematics 2025-08-26 Ksenija Rozman , Primož Šparl

The $P$-partition generating function of a (naturally labeled) poset $P$ is a quasisymmetric function enumerating order-preserving maps from $P$ to $\mathbb{Z}^+$. Using the Hopf algebra of posets, we give necessary conditions for two…

Combinatorics · Mathematics 2019-09-17 Ricky Ini Liu , Michael Weselcouch

We create a framework for studying symmetric chain decompositions of families of finite posets based on the geometry of polytopes. Our framework unifies almost all known results regarding symmetric chain decompositions of the Young posets…

Combinatorics · Mathematics 2017-06-07 Stefan David , Hunter Spink , Marius Tiba

Motivated by recent work on mixtures of classical and free probabilities, we introduce and study the notion of $\epsilon$-noncrossing partitions. It is shown that the set of such partitions forms a lattice, which interpolates as a poset…

Combinatorics · Mathematics 2018-12-06 Kurusch Ebrahimi-Fard , Frederic Patras , Roland Speicher

A dominating set $S$ is an Isolate Dominating Set (IDS) if the induced subgraph $G[S]$ has at least one isolated vertex. In this paper, we initiate the study of new domination parameter called, isolate secure domination. An isolate…

Discrete Mathematics · Computer Science 2020-02-14 Jakkepalli Pavan Kumar , P. Venkata Subba Reddy

For a free group automorphism, we prove that its poset of attracting lamination orbits is a canonical invariant of the associated mapping torus. That is, if a free-by-cyclic group splits as a mapping torus in two different ways, then the…

Group Theory · Mathematics 2026-02-12 Spencer Dowdall , Yassine Guerch , Radhika Gupta , Jean Pierre Mutanguha , Caglar Uyanik

We study two new parameters for finite posets motivated by the problem of efficiently determining the set of successors of a given element. A plane map of a poset $P=(X,\leq)$ is an injective mapping of $X$ into the Cartesian plane…

Combinatorics · Mathematics 2026-05-21 Stefan Felsner , Jędrzej Hodor , Giacomo Ortali , Alexander Wolff

Given a directed graph $D$ with transitive closure $\operatorname{tc}(D)$ and path hypergraph $\mathbb{P}(D)$, we study the connections between the (acyclic) reorientation poset of $\operatorname{tc}(D)$, the (acyclic) sourcing poset of…

Combinatorics · Mathematics 2025-08-05 Antoine Abram , Jose Bastidas , Félix Gélinas , Vincent Pilaud , Andrew Sack

Let $\F\subset 2^{[n]}$ be a family of subsets of $\{1,2,..., n\}$. For any poset $H$, we say $\F$ is $H$-free if $\F$ does not contain any subposet isomorphic to $H$. Katona and others have investigated the behavior of $\La(n,H)$, which…

Combinatorics · Mathematics 2008-07-24 Jerrold R. Griggs , Linyuan Lu

A theorem of Ding, Oporowski, Oxley, and Vertigan implies that any sufficiently large twin-free graph contains a large matching, a co-matching, or a half-graph as a semi-induced subgraph. The sizes of these unavoidable patterns are measured…

Computational Complexity · Computer Science 2026-02-10 Jan Dreier , Nikolas Mählmann , Sebastian Siebertz