Marcus and Newman have
made the following conjecture: Let A = (aij) be a n × n nonnegative symmetric
matrix. Then
where
After reducing the conjecture to a standard maximum problem of linear
programming we prove that it holds for n ≦ 3. A counter example shows that for
n ≧ 4 the conjecture is wrong.
We also consider the following conjecture: Let A = (aij) be a n × n nonnegative
symmetric matrix. Then
where
The validity of this conjecture is established in two cases: (1) m up to 5 and any n,
(2) n up to 3 and any m. The general case remains open. We conclude this paper
with two generalizations of the second theorem.
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