Invariance of Hausdorff null-set cardinal invariants for compact Polish spaces

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Let XX be a compact Polish space, let Hs\mathcal{H}^s denote the ss-dimensional Hausdorff measure, and let HDZX\mathrm{HDZ}_X be the corresponding ideal of Hausdorff-dimension-zero subsets of XX. Write HDZ\mathrm{HDZ} for the associated ideal on the standard reference space, and for an ideal I\mathcal{I} let non⁡(I)\operatorname{non}(\mathcal{I}) and cov⁡(I)\operatorname{cov}(\mathcal{I}) denote its uniformity and covering cardinal invariants.

Invariance conjecture. For every compact Polish space XX with

0<Hs(X)<∞0 < \mathcal{H}^s(X) < \infty

for some s>0s>0,

non⁡(HDZX)=non⁡(HDZ)\operatorname{non}(\mathrm{HDZ}_X)=\operatorname{non}(\mathrm{HDZ})

and

cov⁡(HDZX)=cov⁡(HDZ).\operatorname{cov}(\mathrm{HDZ}_X)=\operatorname{cov}(\mathrm{HDZ}).

The claim proposes that these cardinal characteristics do not depend on the particular compact Polish space once it carries a finite, positive Hausdorff measure in some positive dimension. The supplied text establishes the analogous equalities for Euclidean spaces, but gives no resolution of this broader compact-Polish-space assertion.

References

Primary source

Tatsuya Goto, “Cardinal invariants associated with Hausdorff measures”, arXiv:2112.07952 (2021).

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