All Questions
16 questions
2
votes
0
answers
163
views
Generalizing Hall's marriage theorem to non-perfect matchings
Let $G = (X, Y, E)$ be bipartite graph such that $|X|=|Y|=n$.
A matching $M \subseteq E$ is a subset of disjoint edges
(i.e., there does not exist a pair of edges $(x, y) \in M$ and $(x', y') \in M$ ...
- 121
2
votes
0
answers
60
views
Sum of number of perfect matchings and a constant constuction
Suppose we have two bipartite graphs $G_1$ and $G_2$ with perfect matching count $P_1$ and $P_2$ respectively then their disjoint union gives a bipartite graph with perfect matching $P_1P_2$.
Is ...
- 13.9k
8
votes
0
answers
245
views
Sum of perfect matching construction
Suppose we have two bipartite graphs $G_1$ and $G_2$ with perfect matching count $P_1$ and $P_2$ respectively then their disjoint union gives a bipartite graph with perfect matching $P_1P_2$.
Is ...
- 13.9k
5
votes
1
answer
1k
views
Bipartite graph with exactly one perfect matching
$\textbf{Problem:}$ Find all bipartite graphs $G[X,Y]$ satisfying the following properties:
$1.$ $|X|=|Y|$, where $|X|\ge 2$ and $|Y|\ge 2$.
$2.$ All vertices have degree three except for two vertices ...
- 181
1
vote
1
answer
313
views
Unique bipartite perfect matchings and cycles?
Given a graph $G$ which is bipartite and balanced and has unique perfect matching let $G^{e}$ be $G$ without edge $e$. Let $G\cup G_{\pi,\pi'}$ be union of $G$ and $G_{\pi,\pi'}$ where $G_{\pi,\pi'}$ ...
- 13.9k
1
vote
0
answers
112
views
Is there a bipartite graph whose determinant corresponds to number of perfect matchings?
Let $M\in\{0,1\}^{n\times n}$ be a square integer matrix. If we consider $M$ as biadjacency of a balanced bipartite graph on $2n$ vertices having $n$ vertices of color $1$ and $n$ vertices of color $2$...
- 13.9k
1
vote
1
answer
95
views
Maximum number of perfect matchings in a graph of genus $g$ balanced $k$-partite graph
What is the maximum number of perfect matchings a genus $g$ balanced $k$-partite graph (number of vertices for each color in all possible $k$-colorings is within a difference of $1$) can have? I am ...
- 13.9k
7
votes
1
answer
969
views
Graph to Bipartite conversion preserving number of perfect matchings
Given a graph $G$ on $n$ vertices is there a technique to convert to a balanced bipartite graph $B$ with $O(n^c)$ vertices at some fixed $0<c$ in $O(n^{c'})$ time at some fixed $0<c'$ such that ...
- 13.9k
4
votes
2
answers
987
views
Applications of Hafnians
I am learning about Hafnians but I am struggling to find real-world applications of them. I understand the applications of determinants, permanents, and even pfaffians but I am at a loss for Hafnians. ...
- 111
7
votes
0
answers
349
views
Missing count in number of perfect matchings
Let $f(G)$ give number of perfect matchings of a graph $G$.
Denote $\mathcal N_{2n}=\{0,1,2,\dots,n!-1,n!\}$.
Denote collection of all $2n$ vertex balanced bipartite graph to be $\mathcal G_{2n}$.
...
- 13.9k
1
vote
0
answers
166
views
Expected number of perfect matchings in bounded degree bipartite graphs
Consider collection $\mathcal C_{n,n,\Delta}$ of every $2n$ vertex balanced bipartite graph of average degree $\Delta$.
What is the expected number of perfect matching a graph in $\mathcal C_{n,n,\...
- 13.9k
5
votes
3
answers
876
views
On number of perfect matchings
Consider $2n$ vertex balanced bipartite graph.
If total number of edges is $n^2$ then we have $n!$ perfect matchings.
Fix $c\in(0,\frac12)$ and consider collection of $2n$ vertex balanced bipartite ...
- 13.9k
1
vote
0
answers
66
views
Largest number of perfect matchings in bounded genus graphs
What is the largest number of perfect matchings a genus $g$ bipartite graph on $n+m$ vertices have?
- 13.9k
3
votes
1
answer
576
views
Minimum number of perfect matchings in a regular bipartite graph
Is there a lower bound on the number of perfect matchings in a $k$-regular bipartite graph?
One can use Hall's marriage theorem and induction on $k$ to derive the lower bound of $k$. I can't come up ...
- 217
0
votes
1
answer
773
views
Counting matchings in a bipartite matching-covered graph
A graph is called matching-covered if every edge is containd in a perfect matching. (Such graphs are also sometimes called "elementary", e.g. in Chapter 4 of "Matching Theory" by Lovasz & Plummer)....
- 6,962
8
votes
1
answer
2k
views
Condition on a bipartite graph to have an $m$-factor
This might be the most stupid question I am ever posting here: I am asking for a proof or a counterexample to a problem I proposed on MathLinks long ago.
Let $G$ be a bipartite graph, i. e., a graph ...
- 33.8k