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Estimates of the asymptotic Nikolskii constants for spherical polynomials
Journal of Complexity ( IF 1.7 ) Pub Date : 2021-02-02 , DOI: 10.1016/j.jco.2021.101553
Feng Dai , Dmitry Gorbachev , Sergey Tikhonov

Let Πnd denote the space of spherical polynomials of degree at most n on the unit sphere SdRd+1 that is equipped with the surface Lebesgue measure dσ normalized by Sddσ(x)=1. This paper establishes a close connection between the asymptotic Nikolskii constant, L(d)limn1dimΠndsupfΠndfL(Sd)fL1(Sd), and the following extremal problem: Iαinfakjα+1(t)k=1akjα(qα+1,ktqα+1,1)L(R+) with the infimum being taken over all sequences {ak}k=1R such that the infinite series converges absolutely a.e. on R+. Here jα denotes the Bessel function of the first kind normalized so that jα(0)=1, and {qα+1,k}k=1 denotes the strict increasing sequence of all positive zeros of jα+1. We prove that for α0.272, Iα=0qα+1,1jα+1(t)t2α+1dt0qα+1,1t2α+1dt=1F2(α+1;α+2,α+2;qα+1,124). As a result, we deduce that the constant L(d) goes to zero exponentially fast as d: 0.5dL(d)(0.857)d(1+εd)with εd=O(d23).



中文翻译:

球面多项式的渐近Nikolskii常数的估计

Πñd 最多表示度数的球面多项式的空间 ñ 在单位范围内 小号d[Rd+1个 配备了表面勒贝格测度 dσ 归一化 小号ddσX=1个。本文建立了渐近的Nikolskii常数之间的紧密联系,大号dñ1个暗淡ΠñdSUPFΠñdF大号小号dF大号1个小号d 以及以下极端问题: 一世α信息一种ķĴα+1个Ť-ķ=1个一种ķĴαqα+1个ķŤqα+1个1个大号[R+ 将所有序列取下 {一种ķ}ķ=1个[R 使得无穷级数绝对收敛于 [R+。这里Ĵα 表示第一种标准化的贝塞尔函数,因此 Ĵα0=1个, 和 {qα+1个ķ}ķ=1个 表示的所有正零的严格递增顺序 Ĵα+1个。我们证明α-0272一世α=0qα+1个1个Ĵα+1个ŤŤ2个α+1个dŤ0qα+1个1个Ť2个α+1个dŤ=1个F2个α+1个;α+2个α+2个;-qα+1个1个2个4 结果,我们推断出常数 大号d 随着 d05d大号d0857d1个+εd和 εd=Ød-2个3

更新日期:2021-02-02
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