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Given a function f ^, a set A ^ is free for f if fA A is finite. For a class of functions ^, we define ros_ as the smallest size of a family A ^ such that for every f there is a set A A which is free for f, and _ as the smallest size of a family F such that for every A^ there is f such that A is not free for f. We compare several versions of these cardinal invariants with some of the classical cardinal characteristics of the continuum. Using these notions, we partially answer some questions from arXiv: 1911. 01336 math. LO and arXiv: 2004. 01979 math. GN.
Martínez-Celis et al. (Tue,) studied this question.