Generic Strichartz conjecture for the Schrödinger equation on irrational tori

Let d2d\geq 2 and let (β1,,βd)[1,2]d(\beta_1,\dots,\beta_d)\in[1,2]^d be generic, meaning outside a Lebesgue-null set. Define

Δβ=12π(β112++βdd2)\Delta_\beta=\frac{1}{2\pi}\left(\beta_1\partial_1^2+\cdots+\beta_d\partial_d^2\right)

on the square torus Td=[0,1]d\mathbb{T}^d=[0,1]^d. For N1N\geq 1, T1T\geq 1, and ff with Fourier support in the Euclidean ball B(0,N)B(0,N), let

θ(p)={0,p[1,2(d+2)d),d2(p2(d+2)d),p[2(d+2)d,6),2d2,p[6,).\theta(p)=\begin{cases}0,&p\in\left[1,\frac{2(d+2)}{d}\right),\\[2pt]\frac d2\left(p-\frac{2(d+2)}d\right),&p\in\left[\frac{2(d+2)}d,6\right),\\[2pt]2d-2,&p\in[6,\infty). \end{cases}

Generic Strichartz conjecture. For arbitrarily small ε>0\varepsilon>0, one has

eitΔβfLp([0,T]×Td)εNε(1+Nd2d+2p)[1+(TNθ(p))1/p]fL2.\left\|e^{it\Delta_\beta}f\right\|_{L^p([0,T]\times\mathbb{T}^d)}\lesssim_{\varepsilon}N^{\varepsilon}\left(1+N^{\frac d2-\frac{d+2}{p}}\right)\left[1+\left(\frac{T}{N^{\theta(p)}}\right)^{1/p}\right]\|f\|_{L^2}.

Moreover, these estimates are sharp up to factors NεN^{\varepsilon} for arbitrarily small ε\varepsilon. This conjecture predicts the optimal generic-in-parameter long-time Strichartz bounds for Schrödinger evolution on irrational rectangular tori; the use of genericity is justified by metric Diophantine approximation, while the sharpness assertion and the full range of estimates remain open in the stated generality.

Sources & referencesView supporting material

Primary source

Yu Deng, Pierre Germain and Larry Guth, “Strichartz estimates for the Schrodinger equation on irrational tori”, arXiv:1702.05618 (2017).

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