Strichartz conjecture for the nonelliptic Schrödinger equation on irrational tori

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Let Δ~:=12π(∂11+α∂22)\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 i∂tv−Δ~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~f∥Lp([0,T]×T2)≤Cϵ,αNϵ∥f∥L2(T2){T1pfor 2≤p≤4,T1p+N1−4pfor 4≤p≤6,T1pN1−6p+N1−4pfor 6≤p.\|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 2≤p≤42\leq p\leq4 is known when T≥NT\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.

References

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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