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.