Strichartz conjecture for the nonelliptic Schrödinger equation on irrational tori

Let Δ~:=12π(11+α22)\tilde{\Delta}:=\frac{1}{2\pi}(\partial_{11}+\alpha\partial_{22}) on T2\mathbb{T}^2, where α<0\alpha<0 is irrational, and let eitΔ~fe^{it\tilde{\Delta}}f denote the solution to itvΔ~v=0i\partial_t v-\tilde{\Delta}v=0 with initial data ff. Suppose that the Fourier support of ff is contained in [N,N]2[-N,N]^2. The Strichartz conjecture. For irrational α\alpha, one has

eitΔ~fLp([0,T]×T2)Cϵ,αNϵfL2(T2){T1pfor 2p4,T1p+N14pfor 4p6,T1pN16p+N14pfor 6p.\|e^{it\tilde{\Delta}}f\|_{L^p([0,T]\times\mathbb{T}^2)}\leq C_{\epsilon,\alpha}N^{\epsilon}\|f\|_{L^2(\mathbb{T}^2)}\begin{cases}T^{\frac1p}&\text{for }2\leq p\leq4,\\ T^{\frac1p}+N^{1-\frac4p}&\text{for }4\leq p\leq6,\\ T^{\frac1p}N^{1-\frac6p}+N^{1-\frac4p}&\text{for }6\leq p. \end{cases}

The range 2p42\leq p\leq4 is known when TNT\geq N, while the conjecture remains open in the other stated ranges. It is an analogue of the corresponding conjecture for the elliptic Schrödinger equation on irrational tori.

Sources & referencesView supporting material

Primary source

Larry Guth, Dominique Maldague and Changkeun Oh, “l^2 decoupling theorem for surfaces in R^3”, arXiv:2403.18431 (2025).

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