Lower bounds for parameter-dependent oscillatory integrals and Fourier frames on hypersurfaces

Abstract

We prove lower bounds for Fourier transforms of surface measures $$|\widehat{ψ\,dσ}(ξ)| \gtrsim_{ψ, K, σ, R_0} σ(B(p, |ξ|^{-1})), \text{ given }p\in K\Subset\{ψ>0\} ,\ \vec{n}_{p}\parallel ξ,\ |ξ|\ge R_0,$$ on convex hypersurfaces of finite type with at most one vanishing principal curvature at each point. These bounds are uniform in the choice of $p\in K\Subset \{ψ>0\}$ and match the classical upper bound of Bruna-Nagel-Wainger. The key new analytic ingredient is a uniform lower bound for parameter-dependent oscillatory integrals on $\mathbb{R}$ with convex phases. We also give convex examples of finite type with two vanishing principal curvatures for which $$\inf_{p\in K}|\widehat{ψ\,dσ}(R \vec{n}_p)|\lesssim_N R^{-N},\ \text{ for arbitrary fixed } \{0\}\Subset K\Subset\{ψ>0\}.$$ Though the estimate above has its own interest, our original motivation is to study Fourier frames for surface measures. In particular, we show that, if $Γ$ is a closed convex smooth surface in $\mathbb{R}^d, d\geq 2$, of finite type and at most one principal curvature vanishes at each point, then the surface measure on $Γ$ does not admit any Fourier frame. This weakens the non-vanishing curvature condition in a previous result of Iosevich, Lai, the second author, and Wyman. On centrally symmetric surfaces of non-vanishing Gaussian curvature, we obtain more domains without Fourier frames. For example, we show that $\{x\in S^{d-1}:0 0$, which generalizes the result of Chen and the second author on the hemisphere.