The multiplicative bounded-product conjecture

Let ANA\subset\mathbb{N} have positive density with respect to a multiplicative Følner sequence. For an infinite set BNB\subset\mathbb{N} and tNt\in\mathbb{N}, consider

{b1b2t:b1,b2B, b1b2}.\{b_1b_2t:b_1,b_2\in B,\ b_1\ne b_2\}.

Multiplicative bounded-product conjecture. There exist an infinite set BNB\subset\mathbb{N} and tNt\in\mathbb{N} such that

{b1b2t:b1,b2B, b1b2}A.\{b_1b_2t:b_1,b_2\in B,\ b_1\ne b_2\}\subset A.

This is presented as the multiplicative analogue of the positive-density two-fold sumset problem. The source explicitly says it is open.

Sources & referencesView supporting material

Primary source

Bryna Kra, Joel Moreira, Florian K. Richter and Donald Robertson, “Problems on infinite sumset configurations in the integers and beyond”, arXiv:2311.06197 (2025).

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