Shapiro's shadow-domain conjecture for derivatives of polynomial powers

Let PP be a polynomial of degree d3d\geq 3 whose roots are in convex position and do not form a regular polygon. For 0mnd0\leq m\leq nd, set

Qn,m(z)=dmPn(z)dzm,Q_{n,m}(z)=\frac{d^mP^n(z)}{dz^m},

and let ΥP\Upsilon_P be the closure of the union of all roots of these polynomials. For α[0,d]\boldsymbol{\alpha}\in[0,d], define

Fα(z)=zαP(z)P(z).F_{\boldsymbol{\alpha}}(z)=z-\boldsymbol{\alpha}\frac{P(z)}{P'(z)}.

Shapiro's shadow conjecture. The set ΥP\Upsilon_P is a closed domain in the convex hull of the roots of PP; all critical points of PP lie on its boundary; its boundary has no inflection points; and its boundary is contained in the union of all critical values, with respect to zz, of FαF_{\boldsymbol{\alpha}} as α\boldsymbol{\alpha} ranges over [0,d][0,d]. The conjecture describes the geometric shadow formed by roots of derivatives of powers of PP; the supplied text gives no resolution.

Sources & referencesView supporting material

Primary source

Liudmyla Kryvonos, “Open problems on polynomials, their zero distribution and related questions: 2023”, arXiv:2312.07754 (2023).

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