# Multilinear wave estimates

### Multilinear estimates

There are some isolated examples of multilinear estimates that cannot be obtained from linear and bilinear estimates and Holder's inequality. For instance, the inequality

$|\int D^{-a}D_-(u_1 u_2) u_3 u_4 dx dt| <~ ||f_1||_{H^{n/2-a}} ||f_2||_2 ||f_3||_2 ||f_4||_2$

is proven for d = 2 and 3 / 4 < a < 1 in Sb-p.