ELA, Volume 15, pp. 201-209, July 2006, abstract.
Subdirect sums of S-Strictly Diagonally Dominant Matrices
Rafael Bru, Francisco Pedroche, and Daniel B. Szyld
Conditions are given which guarantee that the k-subdirect
sum of S-strictly diagonally dominant matrices (S-SDD)
is also S-SDD. The same situation is analyzed for SDD
matrices. The converse is also studied: given an SDD
matrix C with the structure of a k-subdirect sum and
positive diagonal entries, it is shown that there are
two SDD matrices whose subdirect sum is C.