Singular values of differences of positive semidefinite matrices

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Abstract

Let Mn be the space of n × n complex matrices. For A ∈ Mn, let s(A) ≡ (s1(A), . . . , Sn(A)), where s1(A) ≥ ⋯ ≥ Sn(A) are the singular values of A. We prove that if A, B ∈ Mn are positive semidefinite, then (i) sj(A - B) ≤ sj(A ⊕ B), j = 1,2, . . . , n, and (ii) the weak log-majorization relations s(A-|z|B) ≺wlog s(A+zB) ≺wlog s(A + \z\B) hold for any complex number z. This sharpens some results due to R. Bhatia and F. Kittaneh.

Original languageEnglish
Pages (from-to)819-823
Number of pages5
JournalSIAM Journal on Matrix Analysis and Applications
Volume22
Issue number3
DOIs
StatePublished - Oct 2000
Externally publishedYes

Keywords

  • Majorization
  • Positive semidefinite matrices
  • Singular values
  • Unitarily invariant norms

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