The dimension formula conjecture for self-similar measures

From papers

Let Φ\Phi be an iterated function system, let pp be a probability vector, and let μ\mu be the corresponding self-similar measure. The entropy rate is

h(Φ,p)=limN1NH(X1XN),h(\Phi,p)=\lim_{N\to\infty}\frac{1}{N}H(X_1\circ\cdots\circ X_N),

where X1,X2,X_1,X_2,\ldots are independent random elements of Φ\Phi distributed according to pp, and HH denotes Shannon entropy. The dimension formula conjecture.

dimμ=min(1,h(Φ,p)iΛpilogλi1).\dim \mu=\min\left(1,\frac{h(\Phi,p)}{\sum_{i\in\Lambda}p_i\log|\lambda_i|^{-1}}\right).

This folklore conjecture predicts that the dimension is governed by the entropy rate, capped at the ambient dimension. It is motivated by the similarity dimensions obtained from iterated compositions and collapsing exact overlaps; no resolution status is supplied in the source.

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Primary source

Péter P. Varjú, “Entropy rates in the dimension theory of self-similar measures”, arXiv:2509.22042 (2026).

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