Stack Exchange network consists of 183 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.
@Joonas, I think you need $d \geq 4$. Anyway I'm interested in the case where $d$ is sufficiently large. Chamizo and Iwniec make the claim for $\alpha=d-2$ in the second paragraph in the paper I linked to. The say there is an elementary proof for it and cite the book by Fricker. This is the proof I'm interested in.