Finite-degree hyperbolicity-preserver conjecture for difference operators

Let TT be a constant-coefficient difference operator

T(p(x))=a0p(x)+a1p(x1)++akp(xk).T(p(x))=a_0p(x)+a_1p(x-1)+\cdots+a_kp(x-k).

It acts on hyperbolic polynomials of degree at most mm whose mesh is at least one, where the mesh is the minimum distance between consecutive roots. Finite-degree difference analogue. The operator TT preserves this set if and only if the polynomial T((x)m)T((x)_m) is hyperbolic and has mesh at least one.

This is proposed as a finite-difference analogue of the finite-degree Hermite–Poulain theorem for constant-coefficient differential operators. Its status is open in the supplied source.

Sources & referencesView supporting material

Primary source

P. Brändén, I. Krasikov and B. Shapiro, “Elements of Polya-Schur theory in finite difference setting”, arXiv:1204.2963 (2013).

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