Dimension conservation conjecture for non-degenerate projections

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Let B⊂R3B\subset\mathbb{R}^{3} be an analytic set, and let (ρθ)θ∈U(\rho_{\theta})_{\theta\in U} and (πθ)θ∈U(\pi_{\theta})_{\theta\in U} be non-degenerate families of projections onto lines and planes, respectively. Proposition 1 states that

dim⁡HB≤12  ⟹  dim⁡Hρθ(B)=dim⁡HB\dim_{\mathrm{H}} B\leq \tfrac12\implies \dim_{\mathrm{H}}\rho_{\theta}(B)=\dim_{\mathrm{H}}B

and

dim⁡HB≤1  ⟹  dim⁡Hπθ(B)=dim⁡HB\dim_{\mathrm{H}} B\leq 1\implies \dim_{\mathrm{H}}\pi_{\theta}(B)=\dim_{\mathrm{H}}B

almost surely. Dimension conservation conjecture. In Proposition 1(a), the hypothesis dim⁡HB≤12\dim_{\mathrm{H}} B\leq \tfrac12 can be relaxed to dim⁡HB≤1\dim_{\mathrm{H}} B\leq 1. In part (b), the hypothesis dim⁡HB≤1\dim_{\mathrm{H}} B\leq 1 can be relaxed to dim⁡HB≤2\dim_{\mathrm{H}} B\leq 2. This predicts dimension preservation for almost every projection throughout the full natural ranges suggested by the target dimensions, beyond the currently established thresholds.

References

Primary source

Katrin Fässler and Tuomas Orponen, “On restricted families of projections in R^3”, arXiv:1302.6550 (2014).

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