Optimal weak estimates for Riesz potentials

Abstract

where γ s =2 -s π -n 2 Γ(n-s 2) Γ(s 2). We also consider the behavior of the best constant 𝒞 n,s of weak type estimate for Riesz potentials, and we prove 𝒞 n,s =O(γ s s) as s→0.