 Diophantine frequency vector

A vector $\omega \in {\mathbb{R}}^n$ satisfying $|k\cdot \omega |\ge \gamma |k{|}_1^{-\tau }$ for all nonzero integer vectors $k$, with $\gamma >0$. This excludes resonances and controls the small divisors in analytic cohomological equations on a Diophantine torus. Different choices of norm change the constant but not the nature of the condition.