Statement

Suppose ω:Rd→R≤0\omega:\mathbb R^d\to\mathbb R_{\le0} satisfies the vanishing, three-derivative, and hypotheses of the . Then there is a continuous u:Cd→Ru:\mathbb C^d\to\mathbb R such that

u(x)≤ω(x),u(x)=0(∣x∣≤2),u(x)\le\omega(x),\qquad u(x)=0\quad(|x|\le2),
∣u(x1)−u(x2)∣≤CLip∣x1−x2∣,u(x)≤u(x+iy)≤u(x)+ρ∣y∣,|u(x_1)-u(x_2)|\le C_{\mathrm{Lip}}|x_1-x_2|, \qquad u(x)\le u(x+iy)\le u(x)+\rho|y|,

where CLip,ρ≲dmax⁡(Creg,Cgr)C_{\mathrm{Lip}},\rho\lesssim_d \max(C_{\mathrm{reg}},C_{\mathrm{gr}}).

Why modification is needed

The original weight need not satisfy the transverse Hessian condition in the . A dyadic modification produces a minorant with comparable regularity and controlled line integrals, to which the exact extension applies.

Role

This proposition solves the potential-theoretic half of the multiplier problem. The then replaces uu by the logarithmic size of an .

References
  1. Alex Cohen, “Fractal uncertainty in higher dimensions,” 2024. arXiv record. Relevant: Proposition 2.2 and §§3–4.