Structured Eigenvalue Condition Number and Backward Error of a Class of Polynomial Eigenvalue Problems

  • Authors:
  • Shreemayee Bora

  • Affiliations:
  • shbora@iitg.ac.in

  • Venue:
  • SIAM Journal on Matrix Analysis and Applications
  • Year:
  • 2009

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Abstract

Necessary and sufficient conditions are obtained for simple eigenvalues of complex matrix polynomials with $\star$-even/odd and $\star$-palindromic/antipalindromic structures to have the same normwise condition number with respect to structure preserving and arbitrary perturbations. Here, $\star$ denotes either the transpose $T$ or the conjugate transpose $*$. Exact expressions for the normwise structured condition number of simple eigenvalues of $*$-palindromic/antipalindromic and $T$-even/odd polynomials and tight bounds that localize the structured condition number of simple eigenvalues of $T$-palindromic/antipalindromic and $*$-even/odd polynomials are also obtained. The backward error of complex numbers $z$ as approximate eigenvalues of these polynomials is also considered, and necessary and sufficient conditions are obtained for a given complex number $z$ to have the same structured and unstructured backward errors.