Sharp Strichartz estimates on quadratic irrational tori

We prove sharp $L^{4}$ Strichartz estimates for two-dimensional periodic Schrödinger flows with integral diagonal symbols $ak_{1}^2+bk_2^2$ where $a,b \in \mathbb Z \setminus \{0\}$. The estimates exhibit a sharp arithmetic dichotomy according to whether $-ab$ is a square: for frequencies bounded by