Subdirect sums, hereditary radicals, and structure spaces

Subdirect Sums of Rings

On eigenvalues and eigenvectors of subdirect sums

Some new properties of the eigenvalues of the subdirect sums are presented for the particular case of 1-subdirect sums. In particular, it is shown that if an eigenvalue λ is associated with certain blocks of matrix A or matrix B then λ is also an eigenvalue associated with the 1-subdirect sum A ⊕1 B. Some results concerning eigenvectors of the k-subdirect sum A⊕k B for an arbitrary positive int...

Subdirect sums of doubly diagonally dominant matrices

The problem of when the k-subdirect sum of a doubly diagonally dominant matrix (DDD matrix) is also a DDD matrix is studied. Some sufficient conditions are given. The same situation is analyzed for diagonally dominant matrices and strictly diagonally dominant matrices. Additionally, some conditions are also derived when card(S)>card(S1) which was not studied by Bru, Pedroche and Szyld [Electron...

Note on Subdirect Sums of Rings

where (a) denotes the two-sided ideal of R generated by a. Then J is the Jacobson radical [6 ] of R, and N is the radical of R as defined in [l]. It is well known that J = 0 if and only if R is isomorphic to a subdirect sum of primitive rings, and ^ = 0 if and only if R is isomorphic to a subdirect sum of simple rings with unit element. The above definitions of / and N suggest that it might be ...

Subdirect Sums of S-strictly Diagonally Dominant Matrices *

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. AMS subject classifications...