<p>We give an example of a function <i>f</i> non-vanishing in the closed bidisk together with the affine polynomial minimizing the norm of <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(1-pf\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mn>1</mn> <mo>-</mo> <mi>p</mi> <mi>f</mi> </mrow> </math></EquationSource> </InlineEquation> in the Hardy space of the bidisk among all affine polynomials <i>p</i> and show that this polynomial vanishes inside the bidisk. This function <i>f</i> has a simple form and follows naturally from Bénéteau (Rev Mat Iberoam 35(2):607–642, 2019), where the phenomenon of zeros seeping into the unit disk was already observed for similar minimization problems in one variable. We can then deduce a counterexample to the weakest form of a conjecture due to Shanks that has been open since 1980, with applications that arose from digital filter design.</p>

错误:搜索内容不能为空,请输入英文关键词
错误:关键词超出字数限制,请精简
高级检索

A Counterexample to the Weak Shanks Conjecture

  • Catherine Bénéteau,
  • Dmitry Khavinson,
  • Daniel Seco

摘要

We give an example of a function f non-vanishing in the closed bidisk together with the affine polynomial minimizing the norm of \(1-pf\) 1 - p f in the Hardy space of the bidisk among all affine polynomials p and show that this polynomial vanishes inside the bidisk. This function f has a simple form and follows naturally from Bénéteau (Rev Mat Iberoam 35(2):607–642, 2019), where the phenomenon of zeros seeping into the unit disk was already observed for similar minimization problems in one variable. We can then deduce a counterexample to the weakest form of a conjecture due to Shanks that has been open since 1980, with applications that arose from digital filter design.