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In [[graph theory]], the '''Edmonds matrix''' <math>A</math> of a balanced [[bipartite graph]] <math>G(U, V, E)</math> with [[Set (mathematics)|set]]s of vertices <math>U = \{u_1, u_2, \dots , u_n \}</math> and <math>V = \{v_1, v_2, \dots , v_n\}</math> is defined by
 
:<math> A_{ij} = \left\{ \begin{array}{ll}
  x_{ij} & (u_i, v_j) \in E \\
  0 & (u_i, v_j) \notin E
\end{array}\right.</math>
 
where the ''x''<sub>ij</sub> are indeterminates. One application of the Edmonds matrix of a bipartite graph is that the graph admits a [[perfect matching]] if and only if the polynomial det(''A''<sub>ij</sub>) in the ''x''<sub>ij</sub> is not identically zero. Furthermore, the number of perfect matchings is equal to the number of [[monomials]] in the polynomial det(''A''), and is also equal to the [[permanent]] of ''A''.
 
The Edmonds matrix is named after [[Jack Edmonds]]. The [[Tutte matrix]] is a generalisation to non-bipartite graphs.
 
==References==
*{{cite book|author=R. Motwani, P. Raghavan |title=Randomized Algorithms |url=http://books.google.com/books/cambridge?id=QKVY4mDivBEC&pg=PR5&sig=8KZG5MvVdHKKRcLYdN91fGyIrBQ#PPA167,M1 |publisher=Cambridge University Press|year=1995|page=167}}
*{{cite book|author=Allen B. Tucker|title=Computer Science Handbook|publisher=CRC Press|date=2004|isbn=1-58488-360-X|page=12.19}}
 
{{combin-stub}}
[[Category:Graph theory objects]]
[[Category:Matrices]]

Revision as of 12:58, 30 September 2013

In graph theory, the Edmonds matrix A of a balanced bipartite graph G(U,V,E) with sets of vertices U={u1,u2,,un} and V={v1,v2,,vn} is defined by

Aij={xij(ui,vj)E0(ui,vj)E

where the xij are indeterminates. One application of the Edmonds matrix of a bipartite graph is that the graph admits a perfect matching if and only if the polynomial det(Aij) in the xij is not identically zero. Furthermore, the number of perfect matchings is equal to the number of monomials in the polynomial det(A), and is also equal to the permanent of A.

The Edmonds matrix is named after Jack Edmonds. The Tutte matrix is a generalisation to non-bipartite graphs.

References

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  • 20 year-old Real Estate Agent Rusty from Saint-Paul, has hobbies and interests which includes monopoly, property developers in singapore and poker. Will soon undertake a contiki trip that may include going to the Lower Valley of the Omo.

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