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seen Sep 9 at 15:31

Jul
10
revised Convergence rate of iterated nonlinear equations?
fixed small format error
Jun
19
comment Reference request for: inverse of a non-singular M-matrix has all elements non-negative?
Fan 1958, Theorem 5' in "Topological proofs for certain theorems on matrices with non-negative elements..." is now the earliest reference I can find.
Jun
19
comment Reference request for: inverse of a non-singular M-matrix has all elements non-negative?
Thanks Dmitry. Looking there and the refs given, Fiedler and Ptak 1962 provide a proof without referencing an earlier result, though earlier work by Ostrowski, Fan, Koteljansku and Minkowski are mentioned, and I imagine one of those probably proved this result earlier.
Jun
19
comment Reference request for: inverse of a non-singular M-matrix has all elements non-negative?
Sorry, you're right, now fixed. As you say, it's an old topic. The result may be found in several places but I'd like to reference the original result if possible.
Jun
19
revised Reference request for: inverse of a non-singular M-matrix has all elements non-negative?
added 15 characters in body
Jun
18
asked Reference request for: inverse of a non-singular M-matrix has all elements non-negative?
May
25
comment Perturbed linear system, particular form
Hi Frederico, I was not familiar with the term but from reading Wikipedia en.wikipedia.org/wiki/Stieltjes_matrix yes - sorry, I have added the important point that we may assume A is positive definite, hence is a Stieltjes matrix (and hence an M-matrix). Are relevant results known for such? Thanks for any help.
May
25
revised Perturbed linear system, particular form
clarification
May
25
revised Perturbed linear system, particular form
Minor correction
May
25
revised Perturbed linear system, particular form
added 7 characters in body
May
25
revised Perturbed linear system, particular form
added 29 characters in body
May
25
revised Perturbed linear system, particular form
added 45 characters in body
May
25
asked Perturbed linear system, particular form
May
24
awarded  Tumbleweed
May
17
asked Trying to solve for total derivatives at a stationary point (maybe using the implicit function theorem)
Jun
19
accepted Lower bound for sum of square root of the degrees of a connected graph
Jun
10
comment Lower bound for sum of square root of the degrees of a connected graph
Thanks Gjergji, that's very helpful! Still I wonder if $\left( \sum_{i=1}^n \sqrt d_i \right)^2 \geq kmn$ for some $k$ for all connected simple graphs? Note that for a star graph, which we might suspect is extreme, $k=1$ works.
Jun
10
awarded  Supporter
Jun
10
awarded  Scholar
Jun
10
accepted Reference request: gluing/pasting perfect graphs on a clique?