Furstenberg dimension conjecture for sine wave and circular sets

Let 0<u10<u\leq1 and 0v30\leq v\leq3. A sine wave (u,v)(u,v)-Furstenberg set or circular (u,v)(u,v)-Furstenberg set is a set FR2F\subseteq\mathbb{R}^2 of the type specified in the paper, with parameters uu and vv. Furstenberg dimension conjecture. Such a set should satisfy

dimF{u+v0vu,5u+v30u<v and 2u+v3,u+12u+v>3,\dim F\geq \begin{cases} u+v & 0\leq v\leq u,\\ \frac{5u+v}{3} & 0\leq u<v\text{ and }2u+v\leq3,\\ u+1 & 2u+v>3, \end{cases}

or equivalently

dimFmin{u+v,5u+v3,u+1}.\dim F\geq\min\left\{u+v,\frac{5u+v}{3},u+1\right\}.

This is proposed as a Furstenberg analogue of the restricted projection conjecture. The first case is known, and product-set examples support the u+1u+1 term when 2u+v>32u+v>3; the remaining asserted bounds are not established in the source.

Sources & referencesView supporting material

Primary source

John Green, Terence L. J. Harris, Yumeng Ou, Kevin Ren and Sarah Tammen, “Incidence bounds related to circular Furstenberg sets”, arXiv:2502.10686 (2025).

Additional references

2 papers in this index state this conjecture (2013–2025). The statement above is taken from the most recent of them; the others are arXiv:1309.2372.

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