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arXiv math/0510367math.CA
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关于齐次多项式的Weierstrass型定理

A Weierstrass-type theorem for homogeneous polynomials

David Benko, Andras Kroo

摘要:

由著名的Weierstrass定理可知,R^d中的紧集上的连续函数空间中的代数多项式集是稠密的。本文研究了仅用齐次多项式逼近时密度是否成立的问题。由于齐次多项式的集合是非线性的,这导致非平凡问题。很容易看出:1)密度仅在星状原点对称曲面上成立; 2)至少需要2个齐次多项式进行近似。星形曲面最有趣的特例是凸曲面。第二作者证明了在R^d中原点对称凸曲面上连续的函数可用一对齐次多项式逼近。这一猜想尚未解决,但我们在积极解决这一问题方面取得了实质性进展。特别地,本文证明了上述猜想对1)d=2,2)R^d中具有C^(1+ n)边界的凸曲面成立.

英文摘要:

By the celebrated Weierstrass Theorem the set of algebraic polynomials is dense in the space of continuous functions on a compact set in R^d. In this paper we study the following question: does the density hold if we approximate only by homogeneous polynomials? Since the set of homogeneous polynomials is nonlinear this leads to a nontrivial problem. It is easy to see that: 1) density may hold only on star-like origin-symmetric surfaces; 2) at least 2 homogeneous polynomials are needed for approximation. The most interesting special case of a star-like surface is a convex surface. It has been conjectured by the second author that functions continuous on origin-symmetric convex surfaces in R^d can be approximated by a pair of homogeneous polynomials. This conjecture is not resolved yet but we make substantial progress towards its positive settlement. In particular, it is shown in the present paper that the above conjecture holds for 1) d=2, 2) convex surfaces in R^d with C^(1+epsilon) boundary.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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