The Nearest Real Polynomial with a Real Multiple Zero in a Given Real Interval

  • Authors:
  • Hiroshi Sekigawa

  • Affiliations:
  • NTT Communication Science Laboratories, Nippon Telegraph and Telephone Corporation, Atsugi-shi, Japan 243-0198

  • Venue:
  • Computer Mathematics
  • Year:
  • 2008

Quantified Score

Hi-index 0.00

Visualization

Abstract

Given f茂戮驴 茂戮驴[x] and a closed real interval I, we provide a rigorous method for finding a nearest polynomial with a real multiple zero in I, that is, $\tilde{f}\in\mathbb{R}[x]$ such that $\tilde{f}$ has a multiple zero in Iand $\|f - \tilde{f}\|_\infty$, the infinity norm of the vector of coefficients of , is minimal. First, we prove that if a nearest polynomial exists, there is a nearest polynomial $\tilde{g}\in\mathbb{R}[x]$ such that the absolute value of every coefficient of $f-\tilde{g}$ is $\|f - \tilde{f}\|_\infty$ with at most one exceptional coefficient. Using this property, we construct h茂戮驴 茂戮驴[x] such that a zero of his a real multiple zero 茂戮驴茂戮驴 Iof $\tilde{g}$. Furthermore, we give a rational function whose value at 茂戮驴is $\|f - \tilde{f}\|_\infty$.