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arXiv 1812.09259math.CO
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整数无解集的复杂性

The complexity of solution-free sets of integers

Keith J. Edwards, Steven D. Noble

摘要:

给定一个线性方程L,一个整数集合A是L-自由的,如果A不包含L的任何非平凡解。Meeks和Treglown证明了对于某些类型的线性方程,判定给定的整数集合是否包含给定大小的无解子集是NP完全的。此外,对于包含三个变量的方程,他们证明了确定最大无解子集的大小的问题是APX困难的,并且对于两个这样的方程(表示无和无级数集),确定是否存在至少具有指定比例元素的无解子集的问题也是NP完全的。我们回答了一些问题所提出的米克斯和Treglown,通过扩展上述结果的所有线性方程,并表明,这些问题仍然很难的整数集的元素是多项式有界的大小设置。对于这些结果中的大多数,只要系数不都具有相同的符号,整数就可以都是正的。我们还考虑了一个给定集合的无解子集的计数问题,并证明了这个问题是P-完全的任何线性方程在至少三个变量。

英文摘要:

Given a linear equation L, a set A of integers is L-free if A does not contain any non-trivial solutions to L. Meeks and Treglown showed that for certain kinds of linear equations, it is NP-complete to decide if a given set of integers contains a solution-free subset of a given size. Also, for equations involving three variables, they showed that the problem of determining the size of the largest solution-free subset is APX-hard, and that for two such equations (representing sum-free and progression-free sets), the problem of deciding if there is a solution-free subset with at least a specified proportion of the elements is also NP-complete. We answer a number of questions posed by Meeks and Treglown, by extending the results above to all linear equations, and showing that the problems remain hard for sets of integers whose elements are polynomially bounded in the size of the set. For most of these results, the integers can all be positive as long as the coefficients do not all have the same sign. We also consider the problem of counting the number of solution-free subsets of a given set, and show that this problem is #P-complete for any linear equation in at least three variables.

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