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A Fiedler's type characterization of band matrices

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Summary:Let K be a field and p an integer positive number. We denote by Bpn (K) the set of n-by-n symmetric band matrices of bandwidth 2p − 1, i.e., if A = [aij ] ∈ Bpn (K) then aij = 0 if |i − j| > p − 1. Let b Bpn (K) be the set of matrices from Bpn (K) in which the entries (i, j), |i − j| = p − 1, are different from zero. Let A be a n-by-n symmetric matrix with entries from K; and p such that 3 6 p 6 n. We will show that: rank(A + B) > n − p + 1, for every B ∈ Bp−1 n (K), if and only if A ∈ b Bpn (K).
Main Authors:Bento, Américo
Other Authors:Duarte, António Leal
Subject:Band matrices Rank Completions problems
Year:2004
Country:Portugal
Document type:preprint
Access type:open access
Associated institution:Universidade de Coimbra
Language:English
Origin:Estudo Geral - Universidade de Coimbra
Description
Summary:Let K be a field and p an integer positive number. We denote by Bpn (K) the set of n-by-n symmetric band matrices of bandwidth 2p − 1, i.e., if A = [aij ] ∈ Bpn (K) then aij = 0 if |i − j| > p − 1. Let b Bpn (K) be the set of matrices from Bpn (K) in which the entries (i, j), |i − j| = p − 1, are different from zero. Let A be a n-by-n symmetric matrix with entries from K; and p such that 3 6 p 6 n. We will show that: rank(A + B) > n − p + 1, for every B ∈ Bp−1 n (K), if and only if A ∈ b Bpn (K).