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Schur multiplier characterization of a class of infinite matrices

A. Marcoci, L. Marcoci, L. E. Persson, N. Popa (2010)

Czechoslovak Mathematical Journal

Let B w ( p ) denote the space of infinite matrices A for which A ( x ) p for all x = { x k } k = 1 p with | x k | 0 . We characterize the upper triangular positive matrices from B w ( p ) , 1 < p < , by using a special kind of Schur multipliers and the G. Bennett factorization technique. Also some related results are stated and discussed.

Self-correcting iterative methods for computing 2 -inverses

Stanimirović, Predrag S. (2003)

Archivum Mathematicum

In this paper we construct a few iterative processes for computing { 2 } -inverses of a linear bounded operator. These algorithms are extensions of the corresponding algorithms introduced in [11] and a method from [8]. A few error estimates are derived.

Semi-Symmetric Algebras: General Constructions. Part II

Iliev, Valentin Vankov (2010)

Serdica Mathematical Journal

2000 Mathematics Subject Classification: 15A69, 15A78.In [3] we present the construction of the semi-symmetric algebra [χ](E) of a module E over a commutative ring K with unit, which generalizes the tensor algebra T(E), the symmetric algebra S(E), and the exterior algebra ∧(E), deduce some of its functorial properties, and prove a classification theorem. In the present paper we continue the study of the semi-symmetric algebra and discuss its graded dual, the corresponding canonical bilinear form,...

Sensor Location Problem for a Multigraph

Pilipchuk, L. A., Vishnevetskaya, T. S., Pesheva, Y. H. (2013)

Mathematica Balkanica New Series

MSC 2010: 05C50, 15A03, 15A06, 65K05, 90C08, 90C35We introduce sparse linear underdetermined systems with embedded network structure. Their structure is inherited from the non-homogeneous network ow programming problems with nodes of variable intensities. One of the new applications of the researched underdetermined systems is the sensor location problem (SLP) for a multigraph. That is the location of the minimum number of sensors in the nodes of the multigraph, in order to determine the arcs ow...

Several results on chordal bipartite graphs

Mihály Bakonyi, Aaron Bono (1997)

Czechoslovak Mathematical Journal

The question of generalizing results involving chordal graphs to similar concepts for chordal bipartite graphs is addressed. First, it is found that the removal of a bisimplicial edge from a chordal bipartite graph produces a chordal bipartite graph. As consequence, occurance of arithmetic zeros will not terminate perfect Gaussian elimination on sparse matrices having associated a chordal bipartite graph. Next, a property concerning minimal edge separators is presented. Finally, it is shown that,...

Sharp Upper Bounds on the Signless Laplacian Spectral Radius of Strongly Connected Digraphs

Weige Xi, Ligong Wang (2016)

Discussiones Mathematicae Graph Theory

Let G = (V (G),E(G)) be a simple strongly connected digraph and q(G) be the signless Laplacian spectral radius of G. For any vertex vi ∈ V (G), let d+i denote the outdegree of vi, m+i denote the average 2-outdegree of vi, and N+i denote the set of out-neighbors of vi. In this paper, we prove that: (1) (1) q(G) = d+1 +d+2 , (d+1 ≠ d+2) if and only if G is a star digraph [...] ,where d+1, d+2 are the maximum and the second maximum outdegree, respectively [...] is the digraph on n vertices obtained...

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