On the construction of a family of sets of positive integers closed under taking subsets

Abstract

In the several contexts such as combinatorial number theory, families of sets of positive integers closed under taking subsets have been investigated. Then it is sometimes useful to give bijections between the set of the one-sided infinite sequences on the alphabet set $\{0,1\}$ and such a family of sets. The most typical example is the family of sum-free sets. Although such a kind of families covers a large class of families of sets, there are only a few considerations on bijections for the case where the sum-free property is replaced by another property. In this paper, we explicitly give a bijection and its inverse between the set of one-sided infinite sequences on the alphabet set $\{0,1\}$ and a family of sets which may be contained in a class of families closed under taking subsets. Moreover, we show that some extremal property in a particular family of sets is characterized by a discrete dynamical system based on this kind of bijections.