Dimension conservation conjecture for non-degenerate projections

Let BR3B\subset\mathbb{R}^{3} be an analytic set, and let (ρθ)θU(\rho_{\theta})_{\theta\in U} and (πθ)θU(\pi_{\theta})_{\theta\in U} be non-degenerate families of projections onto lines and planes, respectively. Proposition 1 states that

dimHB12    dimHρθ(B)=dimHB\dim_{\mathrm{H}} B\leq \tfrac12\implies \dim_{\mathrm{H}}\rho_{\theta}(B)=\dim_{\mathrm{H}}B

and

dimHB1    dimHπθ(B)=dimHB\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 dimHB12\dim_{\mathrm{H}} B\leq \tfrac12 can be relaxed to dimHB1\dim_{\mathrm{H}} B\leq 1. In part (b), the hypothesis dimHB1\dim_{\mathrm{H}} B\leq 1 can be relaxed to dimHB2\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.

Sources & referencesView supporting material

Primary source

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

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