共查询到20条相似文献,搜索用时 109 毫秒
1.
具有Gauss测度的Sobolev空间上的函数逼近 总被引:1,自引:0,他引:1
本文讨论了具有Gauss测度的Sobolev空间上的一元周期函数被三角多项式子空间的最佳逼近及被Fourier部分和算子,Vallée—Poussin算子,Ceshxo算子,Abel算子和Jackson算子的逼近,得到了平均误差估计.证明了在平均框架下,在Lq(1≤q〈∞)空间尺度下三角多项式子空间是渐进最优的子空间,但是在L∞空间尺度下,三角多项式子空间不是渐进最优的子空间.还证明了,Fourier部分和算子和Vallée-Poussin算子在Lq(1≤q≤∞)空间尺度下是渐进最优的线性算子.注意到在平均框架以及Lq(1≤q〈∞)空间尺度下,渐进最优的线性算子,如Fourier部分和算子及Vallée—Poussin算子,与最优的非线性算子的逼近效果一样好. 相似文献
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我们研究了由仅有实零点的代数多项式导出的微分算子确定的广义Sobolev类利用指数型整函数作为逼近工具的最佳限制逼近问题.利用Fourier变换和周期化等方法,得到在L_2(R)范数下的广义Sobolev光滑函数类的相对平均宽度和最佳限制逼近的精确常数,以及当0是这个代数多项式的一个至多2重的零点时,得到最佳限制逼近在L_1(R)范数和一致范数下的广义Sobolev类的精确到阶的结果. 相似文献
5.
王香庆 《高校应用数学学报(A辑)》2004,19(4):471-478
在各类Besov空间中建立若干等价关系.文中的定理1是Cohen等人2000年论文中的定理4.2的实质性扩充,定理2将李松1997年论文中的定理7延拓到0
相似文献
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本文利用带权情形Ditzian Totik无滑模与对应的K 泛函的等价Lp 度量中给出了Γ算子线性组合导数的全局逼近的特征刻画 .本文的结果实质性的推广了文 [3]中的主要结果 相似文献
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球面Hardy空间上Riesz平均的逼近 总被引:1,自引:0,他引:1
引进了球面Hrady空间上Riesz平均算子及Peetre K模。讨论了Riesz平均算子在Hardy空间上的逼近性质。证明了Riesz平均算子与Peetre K模的强渐近等价关系。所得结果表明Peetre K模完全刻划了Riesz平均的逼近。 相似文献
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将线性代数中的向量空间投影理论应用到函数最佳逼近,最小二乘法与微分方程Galerkin方法求解问题中,一方面,将不同学科之间交叉融合,开阔学生视野培养学生融会贯通的能力;另外一方面,从几何的角度处理,直观、学生容易理解;从而为从事相关课程教学的老师提供一定的参考. 相似文献
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Xie Xingwu 《大学数学》1998,(4)
本文对[n/n]Padé逼近进行探讨,证明了Pn(x)/Qn(x)是函数f(x)在x=0处的[n/n]Padé逼近,而Qn(x)=Pn(-x)的充要条件是f(x)f(-x)=1,从而使这一类函数的[n/n]Padé逼近计算量减少一半. 相似文献
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WANG HePing ZHANG YanWei & ZHAI XueBo School of Mathematical Sciences Capital Normal University Beijing China 《中国科学 数学(英文版)》2010,(2)
We discuss the best approximation of periodic functions by trigonometric polynomials and the approximation by Fourier partial summation operators, Valle-Poussin operators, Ces`aro operators, Abel opera-tors, and Jackson operators, respectively, on the Sobolev space with a Gaussian measure and obtain the average error estimations. We show that, in the average case setting, the trigonometric polynomial subspaces are the asymptotically optimal subspaces in the L q space for 1≤q ∞, and the Fourier partial summation operators and the Valle-Poussin operators are the asymptotically optimal linear operators and are as good as optimal nonlinear operators in the L q space for 1≤q ∞. 相似文献
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《Journal of Approximation Theory》2003,120(2):185-216
The density of polynomials is straightforward to prove in Sobolev spaces Wk,p((a,b)), but there exist only partial results in weighted Sobolev spaces; here we improve some of these theorems. The situation is more complicated in infinite intervals, even for weighted Lp spaces; besides, in the present paper we have proved some other results for weighted Sobolev spaces in infinite intervals. 相似文献
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Serge Nicaise 《Mathematische Nachrichten》2000,213(1):117-140
In this paper, we give some polynomial approximation results in a class of weighted Sobolev spaces, which are related to the Jacobi operator. We further give some embeddings of those weighted Sobolev spaces into usual ones and into spaces of continuous functions, in order to use the above approximation results in the p‐version (or the spectral method) of some finite or boundary element methods. Finally, two typical examples of the polynomial approximation of some singularities of boundary value problems in polygonal or polyhedral domains are presented. 相似文献
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Sadulla Z. Jafarov 《复变函数与椭圆型方程》2018,63(10):1444-1458
In the present work, we investigate the approximation problems of the functions by Fejér, and Zygmund means of Fourier trigonometric series in weighted Lebesgue spaces with variable exponents and of the functions by Fejér and Abel–Poisson sums of Faber series in weighted Smirnov classes with variable exponents defined on simply connected domains with a Dini-smooth boundary of the complex plane. 相似文献
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We present sharp bounds on the Kolmogorov probabilistic (N,δ)-width and p-average N-width of multivariate Sobolev space with mixed derivative
, equipped with a Gaussian measure μ in
, that is where 1<q<∞,0<p<∞, and ρ>1 is depending only on the eigenvalues of the correlation operator of the measure μ (see (4)). 相似文献
Full-size image (1K)
17.
Let L^2([0, 1], x) be the space of the real valued, measurable, square summable functions on [0, 1] with weight x, and let n be the subspace of L2([0, 1], x) defined by a linear combination of Jo(μkX), where Jo is the Bessel function of order 0 and {μk} is the strictly increasing sequence of all positive zeros of Jo. For f ∈ L^2([0, 1], x), let E(f, n) be the error of the best L2([0, 1], x), i.e., approximation of f by elements of n. The shift operator off at point x ∈[0, 1] with step t ∈[0, 1] is defined by T(t)f(x)=1/π∫0^π f(√x^2 +t^2-2xtcosO)dθ The differences (I- T(t))^r/2f = ∑j=0^∞(-1)^j(j^r/2)T^j(t)f of order r ∈ (0, ∞) and the L^2([0, 1],x)- modulus of continuity ωr(f,τ) = sup{||(I- T(t))^r/2f||:0≤ t ≤τ] of order r are defined in the standard way, where T^0(t) = I is the identity operator. In this paper, we establish the sharp Jackson inequality between E(f, n) and ωr(f, τ) for some cases of r and τ. More precisely, we will find the smallest constant n(τ, r) which depends only on n, r, and % such that the inequality E(f, n)≤ n(τ, r)ωr(f, τ) is valid. 相似文献
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I. I. Sharapudinov 《Mathematical Notes》2000,67(3):389-397
Let
N+2m
={−m, −m+1, …, −1, 0, 1, …,N−1,N, …,N−1+m}. The present paper is devoted to the approximation of discrete functions of the formf :
N+2m
→ ℝ by algebraic polynomials on the grid Ω
N
={0, 1, …,N−1}. On the basis of two systems of Chebyshev polynomials orthogonal on the sets Ω
N+m
and Ω
N
, respectively, we construct a linear operatorY
n+2m, N
=Y
n+2m, N
(f), acting in the space of discrete functions as an algebraic polynomial of degree at mostn+2m for which the following estimate holds (x ε Ω
N
):
whereE
n+m[g,l
2(Ω
N+m
)] is the best approximation of the function
by algebraic polynomials of degree at mostn+m in the spacel
2 (Ω
N+m
) and the function Θ
N, α
(x) depends only on the weighted estimate for the Chebyshev polynomialsτ
k
α,α
(x, N).
Translated fromMatematicheskie Zametki, Vol. 67, No. 3, pp. 460–470, March, 2000. 相似文献
(1) |
(1) |
20.
S. S. Volosivets 《Mathematical Notes》1997,62(3):306-313
In this paper the best polynomial approximation in terms of the system of Faber-Schauder functions in the spaceC
p
[0, 1] is studied. The constant in the estimate of Jackson’s inequality for the best approximation in the metric ofC
p
[0, 1] and the estimate of the modulus of continuity ω1−1/p
are refined.
Translated fromMatematicheskie Zametki, Vol. 62, No. 3, pp. 363–371, September, 1997.
Translated by N. K. Kulman 相似文献