Gaussians never extremize Strichartz inequalities for hyperbolic paraboloids

Emanuel Carneiro, Lucas Oliveira, Mateus Sousa

For $\xi =({\xi }_1,{\xi }_2,\dots ,{\xi }_d)\in {\mathbb{R}}^d$ let $Q(\xi ):={\sum }_{j=1}^d{\sigma }_j{\xi }_j^2$ be a quadratic form with signs ${\sigma }_j\in \{\pm 1\}$ not all equal. Let $S \subset \mathbb{R}^{d…