arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1303.0605math.NT
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广义和大于差集大类的显式构造

Explicit Constructions of Large Families of Generalized More Sums Than Differences Sets

Steven J. Miller, Sean Pegado, Luc Robinson

摘要:

和大于差(MSTD)集合是包含在{0,.,n-1},其和集A+A大于其差集A-A。虽然已知当n趋于无穷大时,{0,.,n-1}是MSTD集,证明这一点的方法是概率性的,并且不会产生好的、明确的构造。最近,Miller,Orosz和Scheinerman给出了MSTD集的一个大家族的显式构造;虽然它们的密度小于一个正的百分比,但它们的家族在{0,.对于某些C>0,n-1}至少为C/n^4,明显大于先前的构造,其数量级为1 / 2^{n/2}。我们推广了他们的方法,并明确地构造了一个大的集合族A,|A+A +A+| > |(A+A)-(A+A)|.额外的和与差使我们比米勒、奥罗兹和谢内曼的研究有更大的自由度,我们发现,对于任何n>0,这样的集合的密度至少是C / n^n。在构造这样的集合的过程中,我们发现对于任何整数k,存在A,使得|A+A +A+| - |A+A-A-A| = k,并表明这样一个集合的最小跨度是30。

英文摘要:

A More Sums Than Differences (MSTD) set is a set of integers A contained in {0, ..., n-1} whose sumset A+A is larger than its difference set A-A. While it is known that as n tends to infinity a positive percentage of subsets of {0, ..., n-1} are MSTD sets, the methods to prove this are probabilistic and do not yield nice, explicit constructions. Recently Miller, Orosz and Scheinerman gave explicit constructions of a large family of MSTD sets; though their density is less than a positive percentage, their family's density among subsets of {0, ..., n-1} is at least C/n^4 for some C>0, significantly larger than the previous constructions, which were on the order of 1 / 2^{n/2}. We generalize their method and explicitly construct a large family of sets A with |A+A+A+A| > |(A+A)-(A+A)|. The additional sums and differences allow us greater freedom than in Miller, Orosz and Scheinerman, and we find that for any epsilon>0 the density of such sets is at least C / n^epsilon. In the course of constructing such sets we find that for any integer k there is an A such that |A+A+A+A| - |A+A-A-A| = k, and show that the minimum span of such a set is 30.

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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