Point-to-set Principle and Constructive Dimension Faithfulness
For researchers in fractal geometry and algorithmic information theory, this work unifies and extends point-to-set principles and provides an information-theoretic proof of a known result, though the advance is incremental.
The paper introduces constructive Φ-dimension, an effective version of Hausdorff Φ-dimension, and proves a point-to-set principle for Φ-dimension that generalizes principles for Hausdorff dimension, continued fraction dimension, and Cantor coverings. It provides a Kolmogorov complexity characterization and establishes necessary and sufficient conditions for faithfulness of Cantor coverings, showing equivalence between Hausdorff and constructive faithfulness.
Hausdorff $Φ$-dimension is a notion of Hausdorff dimension developed using a restricted class of coverings of a set. We introduce an effective version of Hausdorff $Φ$-dimension, which we call constructive $Φ$-dimension. We prove a point-to-set principle for $Φ$-dimension, through which we get point-to-set principles for Hausdorff dimension, continued fraction dimension, and dimension of Cantor coverings as special cases. We also provide a Kolmogorov complexity characterization of constructive $Φ$-dimension. A class of covering sets $Φ$ is said to be ``faithful'' to Hausdorff dimension if the $Φ$-dimension and Hausdorff dimension coincide for every set. Similarly, $Φ$ is said to be ``faithful'' to constructive dimension if the constructive $Φ$-dimension and constructive dimension coincide for every set. We derive the necessary and sufficient conditions for the constructive dimension faithfulness of the coverings generated by the Cantor series expansion, based on the terms of the expansion. Using the point-to-set principle for Cantor coverings and a new technique for the construction of sequences satisfying a certain Kolmogorov complexity condition, we show that the notions of ``faithfulness'' of Cantor coverings at the Hausdorff and constructive levels are equivalent. Hence we show the necessary and sufficient conditions for Hausdorff dimension faithfulness of Cantor coverings, thereby giving an information theoretic proof of the result by Albeverio, Ivanenko, Lebid, and Torbin.