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SUM AND DIFFERENCE FREE SETS

机译:总和和差额免费集

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In this paper we prove that if X is an uncountable subset of the reals and κ is a cardinal smaller than the cardinality of the set X, then the algebraic difference X - X of the set X is not a finite union of κ sum free or κ difference free sets. An application of the above result is that for any function f : R → {1, 2,..., n} and for each cardinal λ < 2~ω, the set of all x such that |{h > 0 : f(x - h) = f (x + h)}| ≥ λ is of the size of the continuum. Among other things, we show that a finite union of countably many translates of 2~ω difference free subsets of the reals is not residual in an interval. In the above statement, "countably many" can be replaced by "fewer than continuum many" provided that 2~ω is a regular cardinal.
机译:在本文中,我们证明了:如果X是实数的不可数子集,并且κ是小于集合X的基数的基数,那么集合X的代数差X-X并不是κ和自由的有限并集或κ差异自由集。上述结果的应用是,对于任何函数f:R→{1,2,...,n}和每个基数λ<2〜ω,所有x的集合使得| {h> 0:f (x-h)= f(x + h)} | ≥λ是连续体的大小。除其他事项外,我们表明,实数的2〜ω个无差子集的无数次平移的有限并集在间隔中不是残差的。在上面的陈述中,只要2〜ω是正则基数,就可以用“少于连续许多”来代替“很多”。

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