Equality of density cardinals for singleton targets in the unit interval

For r(0,1)r\in(0,1), let dd{r},all{\mathfrak{dd}}_{\{r\},{\mathsf{all}}} denote the corresponding density cardinal; the same notation is used when all{\mathsf{all}} is replaced by [0,1][0,1], {0,1}\{0,1\}, or (0,1)(0,1). Singleton-target density-cardinal conjecture.

dd{r},all=dd{1/2},all{\mathfrak{dd}}_{\{r\},{\mathsf{all}}}={\mathfrak{dd}}_{\{1/2\},{\mathsf{all}}}

for all r(0,1)r\in(0,1), and likewise for each of those replacements of all{\mathsf{all}}. The paper notes that the equality is not known, although symmetry gives equality between the parameters rr and 1r1-r; these cardinals can also be strictly smaller than non(M){\mathsf{non}}({\mathcal M}).

Sources & referencesView supporting material

Primary source

Christina Brech, Jörg Brendle and Márcio Telles, “Density cardinals”, arXiv:2410.21102 (2024).

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