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On an Algorithm of G. Birkhoff Concerning Doubly Stochastic Matrices

Published online by Cambridge University Press:  20 November 2018

Diane M. Johnson
Affiliation:
University of Manitoba
A. L. Dulmage
Affiliation:
University of Manitoba
N. S. Mendelsohn
Affiliation:
University of Manitoba
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In [1] G. Birkhoff stated an algorithm for expressing a doubly stochastic matrix as an average of permutation matrices. In this note we prove two graphical lemmas and use these to find an upper bound for the number of permutation matrices which the Birkhoff algorithm may use.

A doubly stochastic matrix is a matrix of non-negative elements with row and column sums equal to unity and is there - fore a square matrix. A permutation matrix is an n × n doubly stochastic matrix which has n2-n zeros and consequently has n ones, one in each row and one in each column. It has been shown by Birkhoff [1],Hoffman and Wielandt [5] and von Neumann [7] that the set of all doubly stochastic matrices, considered as a set of points in a space of n2 dimensions constitute the convex hull of permutation matrices.

Type
Research Article
Copyright
Copyright © Canadian Mathematical Society 1960

References

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