Absolute continuity conjecture for contracting-on-average self-similar measures

Let GG be the group acting on Rd\mathbb{R}^d in the self-similar setting, and let ν\nu be the associated stationary measure of a finitely supported, contracting on average and irreducible probability measure μ\mu on GG without a common fixed point. Write hμh_{\mu} for the entropy of μ\mu and χμ\chi_{\mu} for its Lyapunov exponent. Absolute continuity conjecture. Then ν\nu is absolutely continuous if

hμχμ>d.\frac{h_{\mu}}{|\chi_{\mu}|}>d.

This conjecture predicts absolute continuity in the dimension-saturated regime beyond the natural entropy-to-Lyapunov threshold. The preceding dimension results establish the expected dimension formula under additional separation or arithmetic hypotheses, but the stated absolute-continuity implication is presented as folklore and remains open in this generality.

Sources & referencesView supporting material

Primary source

Samuel Kittle and Constantin Kogler, “On absolute continuity of inhomogeneous and contracting on average self-similar measures”, arXiv:2409.18936 (2025).

Additional references

3 papers in this index state this conjecture (2008–2024). The statement above is taken from the most recent of them; the others are arXiv:2012.15528, arXiv:0803.3094.

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