Length Sharp stability of log-Sobolev and Moser-Onofri inequalities on the sphere *

In this paper, we are concerned with the stability problem for endpoint conformally invariant cases of the Sobolev inequality on the sphere Sn. Namely, we will establish the stability for Beckner's log-Sobolev inequality and Beckner's MoserOnofri inequality on the sphere. We also prove that the sharp constant of global stability for the log-Sobolev inequality on the sphere Sn must be strictly smaller than the sharp constant of local stability for the same inequality. Furthermore, we also derive the non-existence of the global stability for MoserOnofri inequality on the sphere Sn.& COPY; 2023 Elsevier Inc. All rights reserved.