Vania Mascioni

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Abstract. Let Pn be the complex vector space of all polynomials of degree at most n. We give several characterizations of the linear operators T : Pn → Pn for which there exists a constant C > 0 such that for all nonconstant f ∈ Pn there exist a root u of f and a root v of Tf with |u−v| ≤ C. We prove that such perturbations leave the degree unchanged and,(More)
We provide a unified, elementary, topological approach to the classical results stating the continuity of the complex roots of a polynomial with respect to its coefficients, and the continuity of the coefficients with respect to the roots. In fact, endowing the space of monic polynomials of a fixed degree n and the space of n roots with suitable topologies,(More)
In the context of finite metric spaces with integer distances, we investigate the new Ramsey-type question of how many points can a space contain and yet be free of equilateral triangles. In particular, for finite metric spaces with distances in the set {1, . . . , n}, the number Dn is defined as the least number of points the space must contain in order to(More)
Given a polynomial p of degree n ≥ 2 and with at least two distinct roots let Z(p) = {z : p(z) = 0}. For a fixed root α ∈ Z(p) we define the quantities ω(p, α) := min { |α − v| : v ∈ Z(p) \ {α} } and τ(p, α) := min { |α − v| : v ∈ Z(p′) \ {α} } . We also define ω(p) and τ(p) to be the corresponding minima of ω(p, α) and τ(p, α) as α runs over Z(p). Our main(More)
We prove a tight inequality of non-exponential type for a weighted geometric mean commonly appearing when using Stirling’s approximation (also frequently studied in its logarithmic form when computing entropies). As an application we prove corollaries involving binomial coefficients. 1. The main inequalities If r ∈ R\ {0} , in the notation from Mitrinović’s(More)
The celebrated Gauss-Lucas theorem states that all the roots of the derivative of a complex non-constant polynomial p lie in the convex hull of the roots of p, called the Lucas polygon of p. We improve the Gauss-Lucas theorem by proving that all the nontrivial roots of p′ lie in a smaller convex polygon which is obtained by a strict contraction of the Lucas(More)