Edrei–Saff–Varga modified width conjecture

Let ff be an entire function of positive, finite order λ\lambda, and let pn(z)p_n(z) denote its nthn^\text{th} partial sum. Edrei–Saff–Varga's modified width conjecture. There exist an infinite sequence of positive integers NN and finitely many exceptional arguments θ1,θ2,,θq\theta_1,\theta_2,\ldots,\theta_q such that the following hold: for every argument θθj\theta\ne\theta_j, j=1,2,,qj=1,2,\ldots,q, there is a positive sequence ρn\rho_n, nNn\in N, with ρn\rho_n\to\infty and ρn=O(n2/λ)\rho_n=O(n^{2/\lambda}), for which, for every fixed ϵ>0\epsilon>0, the number of zeros of pn(z)p_n(z) in

zρneiθρnn1+ϵ\left|z-\rho_ne^{i\theta}\right|\leq\rho_nn^{-1+\epsilon}

tends to infinity as nn\to\infty, nNn\in N; and for every exceptional argument θj\theta_j, there is an integer m2m\geq2 and a positive sequence ρn\rho_n, nNn\in N, with ρn\rho_n\to\infty and ρn=O(n2/(λm))\rho_n=O(n^{2/(\lambda m)}), for which, for every fixed ϵ>0\epsilon>0, the number of zeros of pn(z)p_n(z) in

zρneiθjρnn1/m+ϵ\left|z-\rho_ne^{i\theta_j}\right|\leq\rho_nn^{-1/m+\epsilon}

tends to infinity as nn\to\infty, nNn\in N. The modified conjecture describes dense clustering of zeros in all but finitely many directions, with slower concentration allowed in exceptional directions associated with maximal exponential growth; its resolution is not specified in the source.

Sources & referencesView supporting material

Primary source

Antonio R. Vargas, “Newman-Rivlin asymptotics for partial sums of power series”, arXiv:1503.04262 (2015).

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