arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 0911.3473cs.CC
收藏

多项式阈值函数:结构、逼近与伪随机性

Polynomial Threshold Functions: Structure, Approximation and Pseudorandomness

Ido Ben-Eliezer, Shachar Lovett, Ariel Yadin

摘要:

研究了多项式阈值函数的计算能力,即布尔立方体上实多项式的阈值函数。我们提供了两个新的结果,这个模型的计算能力的边界。我们的第一个结果表明,低次多项式阈值函数不能近似任何具有许多影响变量的函数。我们提供了一对夫妇的例子,这种技术产生紧密的近似边界。我们的第二个结果涉及到构建伪随机发生器愚弄低次多项式阈值函数。这个问题最近受到了关注,Diakonikolas等人证明了$k$独立性足以欺骗线性阈值函数。我们证明了任何低次多项式阈值函数,它可以表示为一个函数的一个小数目的线性阈值函数,也可以愚弄$k$明智的独立性。我们认为这是愚弄一般多项式阈值函数的重要一步,我们讨论了一个合理的方法,实现这一目标的基础上,我们的技术。我们的结果结合了实逼近理论,超压缩不等式和概率方法的工具。特别是,我们开发了几个新的工具,在近似理论,这可能是独立的利益。

英文摘要:

We study the computational power of polynomial threshold functions, that is, threshold functions of real polynomials over the boolean cube. We provide two new results bounding the computational power of this model. Our first result shows that low-degree polynomial threshold functions cannot approximate any function with many influential variables. We provide a couple of examples where this technique yields tight approximation bounds. Our second result relates to constructing pseudorandom generators fooling low-degree polynomial threshold functions. This problem has received attention recently, where Diakonikolas et al proved that $k$-wise independence suffices to fool linear threshold functions. We prove that any low-degree polynomial threshold function, which can be represented as a function of a small number of linear threshold functions, can also be fooled by $k$-wise independence. We view this as an important step towards fooling general polynomial threshold functions, and we discuss a plausible approach achieving this goal based on our techniques. Our results combine tools from real approximation theory, hyper-contractive inequalities and probabilistic methods. In particular, we develop several new tools in approximation theory which may be of independent interest.

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。

↑