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arXiv 1310.2017math.COcs.CCmath.MG
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布尔立方体与Hamming球的双Lipschitz双射

Bi-Lipschitz Bijection between the Boolean Cube and the Hamming Ball

Itai Benjamini, Gil Cohen, Igor Shinkar

摘要:

我们构造了一个从布尔立方体到等体积汉明球的双Lipschitz双射。更精确地说,我们证明了对于所有偶数n,存在从n维布尔立方体到嵌入在(n+1)维布尔立方体中的等体积汉明球的显式双射f,使得对于所有x和y,距离(x,y)/ 5 <=距离(f(x),f(y))<= 4距离(x,y),其中距离(,)表示汉明距离。特别地,这意味着汉明球是双李普希茨传递的。这一结果对Lovett和Viola [CC 2012]的一个开放问题给出了强烈的否定回答,他们在低级别复杂性类中的抽样分布的背景下提出了这个问题。概念上的含义是,在抽样分布的背景下证明下界的问题将需要一些新的想法,超出了Boppana [IPL 97]的基于灵敏度的结构结果。我们进一步研究了映射f,并证明了它(及其逆)在DLOGTIME-均匀TC 0中是可计算的,但在AC 0中不可计算。此外,我们证明,f是“近似本地”的意义上说,所有的,但最后一个输出位的f基本上是由一个单一的输入位。

英文摘要:

We construct a bi-Lipschitz bijection from the Boolean cube to the Hamming ball of equal volume. More precisely, we show that for all even n there exists an explicit bijection f from the n-dimensional Boolean cube to the Hamming ball of equal volume embedded in (n+1)-dimensional Boolean cube, such that for all x and y it holds that distance(x,y) / 5 <= distance(f(x),f(y)) <= 4 distance(x,y) where distance(,) denotes the Hamming distance. In particular, this implies that the Hamming ball is bi-Lipschitz transitive. This result gives a strong negative answer to an open problem of Lovett and Viola [CC 2012], who raised the question in the context of sampling distributions in low-level complexity classes. The conceptual implication is that the problem of proving lower bounds in the context of sampling distributions will require some new ideas beyond the sensitivity-based structural results of Boppana [IPL 97]. We study the mapping f further and show that it (and its inverse) are computable in DLOGTIME-uniform TC0, but not in AC0. Moreover, we prove that f is "approximately local" in the sense that all but the last output bit of f are essentially determined by a single input bit.

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