The absolute-continuity conjecture for multiplicative convolutions of self-similar measures

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Let μ1,…,μk\mu_1,\dots,\mu_k be self-similar measures supported in (0,∞)(0,\infty) with

∑i=1kκ2(μi)>1.\sum_{i=1}^k\kappa_2(\mu_i)>1.

Their multiplicative convolution μ1⋅μ2⋯μk\mu_1\cdot \mu_2 \dotsb \mu_k is the pushforward of the product measure under multiplication.

Multiplicative-convolution conjecture. The measure μ1⋅μ2⋯μk\mu_1\cdot \mu_2 \dotsb \mu_k is absolutely continuous with respect to Lebesgue measure.

The conjecture is motivated by the corresponding positive-measure problem for arithmetic products and by the paper's Fourier-decay approach. The supplied evidence resolves it for certain specific self-similar measures, including the middle-third Cantor measure, but not in the stated generality.

References

Primary source

Amlan Banaji and Han Yu, “Fourier transform of nonlinear images of self-similar measures: quantitative aspects”, arXiv:2503.07508 (2026).

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