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Deformation of roots of polynomials via fractional derivatives. (English) Zbl 1261.65046

Summary: We first recall the main features of fractional calculus. In the expression of fractional derivatives of a real polynomial \(f(x)\), we view the order of differentiation \(q\) as a new indeterminate; then we define a new bivariate polynomial \(P_{f}(x,q)\). For \(0\leq q\leq 1, P_{f}(x,q)\) defines a homotopy between the polynomials \(f(x)\) and \(xf^{\prime}(x)\). Iterating this construction, we associate to \(f(x)\) a plane spline curve, called the stem of \(f\). Stems of classic random polynomials exhibits intriguing patterns; moreover in the complex plane \(P_{f}(x,q)\) creates an unexpected correspondence between the complex roots and the critical points of \(f(x)\). We propose 3 conjectures to describe and explain these phenomena. Illustrations are provided relying on the computer algebra system Maple.

MSC:

65H04 Numerical computation of roots of polynomial equations
65D07 Numerical computation using splines
26A33 Fractional derivatives and integrals
12D10 Polynomials in real and complex fields: location of zeros (algebraic theorems)
65E05 General theory of numerical methods in complex analysis (potential theory, etc.)
30C15 Zeros of polynomials, rational functions, and other analytic functions of one complex variable (e.g., zeros of functions with bounded Dirichlet integral)
65H20 Global methods, including homotopy approaches to the numerical solution of nonlinear equations
68W30 Symbolic computation and algebraic computation

Software:

Maple
Full Text: DOI