An application of kissing numbers in sum-product estimates

Abstract

The boundedness of the kissing numbers of convex bodies has been known to Hadwiger for long. We present an application of it to the sum-product estimate $$\max(|\mathcal{A}+\mathcal{A}|,|\mathcal{A}\mathcal{A}|)\gg\dfrac{|\mathcal{A}|^{4/3}}{\lceil\log|\mathcal{A}|\rceil^{1/3}}$$ for finite sets $\mathcal{A}$ of quaternions and of a certain family of well-conditioned matrices.