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A graph $G$ is a brick if it is 3-connected and $G-\{u,v\}$ has a perfect matching for any two distinct vertices $u$ and $v$ of $G$. A brick $G$ is solid if for any two vertex disjoint odd cycles $C_1$ and $C_2$ of $G$, $G-(V(C_1)\cup…

Combinatorics · Mathematics 2025-07-30 Yipei Zhang , Xiumei Wang

A connected graph G with at least two vertices is matching covered if each of its edges lies in a perfect matching. We say that an edge e in a matching covered graph G is removable if G-e is matching covered. A pair {e; f} of edges of a…

Combinatorics · Mathematics 2025-06-03 Xiaoling He , Fuliang Lu , Jinxin Xue

Lov\'asz (1987) proved that every matching covered graph $G$ may be uniquely decomposed into a list of bricks (nonbipartite) and braces (bipartite); we let $b(G)$ denote the number of bricks. An edge $e$ is removable if $G-e$ is also…

Combinatorics · Mathematics 2026-05-22 Nishad Kothari , Marcelo H. de Carvalho , Cláudio L. Lucchesi , Charles H. C. Little

A nontrivial connected graph is matching covered if each edge belongs to some perfect matching. For most problems pertaining to perfect matchings, one may restrict attention to matching covered graphs; thus, there is extensive literature on…

Combinatorics · Mathematics 2025-11-10 Rohinee Joshi , Santhosh Raghul , Nishad Kothari

A {\em brick} is a non-bipartite matching covered graph without non-trivial tight cuts. Bricks are building blocks of matching covered graphs. We say that an edge $e$ in a brick $G$ is {\em $b$-invariant} if $G-e$ is matching covered and a…

Combinatorics · Mathematics 2020-02-14 Fuliang Lu , Xing Feng , Yan Wang

{ An edge $e$ in a matching covered graph $G$ is {\em removable} if $G-e$ is matching covered, which was introduced by Lov\'asz and Plummer in connection with ear decompositions of matching covered graphs. A {\it brick}} is a non-bipartite…

Combinatorics · Mathematics 2024-01-17 Lu Fuliang , Qian Jianguo

A graph $G$ is a brick if it is 3-connected and $G-\{u,v\}$ has a perfect matching for any two distinct vertices $u$ and $v$ of $G$. Lucchesi and Murty proposed a problem concerning the characterization of bricks, distinct from $K_4$,…

Combinatorics · Mathematics 2025-09-30 Yipei Zhang , Xiumei Wang

A graph $G$ is called matching covered if all of its edges are contained in some perfect matching of $G$. Furthermore, a cycle $C \subseteq G$ is called conformal if $G - V(C)$ has a perfect matching and $G$ itself is called cycle-conformal…

Combinatorics · Mathematics 2026-02-10 Maximilian Gorsky , Clemens Kuske

For a subset $X$ of the vertex set $\VV(\GG)$ of a graph $\GG$, we denote the set of edges of $\GG$ which have exactly one end in $X$ by $\partial(X)$ and refer to it as the cut of $X$ or edge cut $\partial(X)$. A graph $\GG=(\VV,\EE)$ is…

Combinatorics · Mathematics 2025-10-30 Koustav De

An edge e in a matching covered graph G is removable if G-e is matching covered; a pair {e; f} of edges of G is a removable doubleton if G-e-f is matching covered, but neither G-e nor G-f is. Removable edges and removable doubletons are…

Combinatorics · Mathematics 2024-10-29 Fuliang Lu , Jinxin Xue

An edge $e$ of a matching covered graph $G$ is removable if $G-e$ is also matching covered. The notion of removable edge arises in connection with ear decompositions of matching covered graphs introduced by Lov\'asz and Plummer. A…

Combinatorics · Mathematics 2024-06-04 Yipei Zhang , Fuliang Lu , Xiumei Wang , Jinjiang Yuan

A connected graph G is matching covered if every edge lies in some perfect matching of G. Lovasz proved that every matching covered graph G can be uniquely decomposed into a list of bricks (nonbipartite) and braces (bipartite) up to…

Combinatorics · Mathematics 2024-11-27 Yaxian Zhang , Fuliang Lu , Heping Zhang

A matching covered graph $G$ is minimal if for each edge $e$ of $G$, $G-e$ is not matching covered. An edge $e$ of a matching covered graph $G$ is removable if $G-e$ is also matching covered. Thus a matching covered graph is minimal if and…

Combinatorics · Mathematics 2024-05-28 Yipei Zhang , Xiumei Wang , Jinjiang Yuan , C. T. Ng , T. C. E. Cheng

The perfect matching polytope, i.e. the convex hull of (incidence vectors of) perfect matchings of a graph is used in many combinatorial algorithms. Kotzig, Lov\'asz and Plummer developed a decomposition theory for graphs with perfect…

Combinatorics · Mathematics 2019-03-01 Isabel Beckenbach , Meike Hatzel , Sebastian Wiederrecht

A $3$-connected graph $G$ is a brick if, for any two vertices $u$ and $v$, the graph $G-\{u,v\}$ has a perfect matching. Deleting an edge $e$ from a brick $G$ results in a graph with zero, one or two vertices of degree two. The…

Combinatorics · Mathematics 2026-05-21 Nishad Kothari

The (Perfect) Matching Cut problem is to decide if a connected graph has a (perfect) matching that is also an edge cut. The Disconnected Perfect Matching problem is to decide if a connected graph has a perfect matching that contains a…

Combinatorics · Mathematics 2023-11-08 Carl Feghali , Felicia Lucke , Daniel Paulusma , Bernard Ries

A connected graph $G$, of order two or more, is matching covered if each edge lies in some \pema. The tight cut decomposition of a matching covered graph $G$ yields a list of bricks and braces; as per a theorem of Lov{\'a}sz~\cite{lova87},…

Combinatorics · Mathematics 2019-12-18 Fuliang Lu , Nishad Kothari , Xing Feng , Lianzhu Zhang

For a connected graph $G=(V,E)$, a matching $M\subseteq E$ is a matching cut of $G$ if $G-M$ is disconnected. It is known that for an integer $d$, the corresponding decision problem Matching Cut is polynomial-time solvable for graphs of…

Combinatorics · Mathematics 2022-07-18 Felicia Lucke , Daniël Paulusma , Bernard Ries

An edge cut C of a graph G is tight if |C \M| = 1 for every perfect matching M of G. Barrier-cuts and 2-separation cuts, also referred to as ELP-cuts, are two important types of tight cuts in matching covered graphs. Edmonds, Lovasz and…

Combinatorics · Mathematics 2026-05-26 Fuliang Lu , Fengming Dong

The NP-complete problem Matching Cut is to decide if a graph has a matching that is also an edge cut of the graph. We prove new complexity results for Matching Cut restricted to $H$-free graphs, that is, graphs that do not contain some…

Combinatorics · Mathematics 2022-07-15 Felicia Lucke , Daniël Paulusma , Bernard Ries
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