Polynomial concentration conjecture for the number of real zeros of Kac polynomials

From papers

Let fn(x)=i=0nξixif_n(x)=\sum_{i=0}^{n}\xi_i x^i be a Kac polynomial whose independent coefficients ξi\xi_i have mean zero and variance one, and let Nn(R)N_n(\mathbb R) denote its number of real roots. Under mild conditions on the coefficients, for every ε>0\varepsilon>0 there exist constants c,C>0c,C>0 such that, for all nn,

1CnCP(Nn(R)ENn(R)εlogn)Cnc.\frac{1}{C}n^{-C}\leq \mathbb P\left(\left|N_n(\mathbb R)-\mathbb E N_n(\mathbb R)\right|\geq \varepsilon\log n\right)\leq Cn^{-c}.

Concentration conjecture. Under mild conditions, the probability that the number of real zeros deviates from its expectation by at least εlogn\varepsilon\log n is bounded above and below by polynomial functions of nn as displayed above. This would provide quantitative concentration estimates complementing the known logarithmic asymptotics for the expected number of real roots and the central limit theorem for Nn(R)N_n(\mathbb R).

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Sources & referencesView supporting material

Primary source

Van Hao Can and Oanh Nguyen, “Concentration inequalities for the number of real zeros of Kac polynomials”, arXiv:2311.15446 (2024).

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