Sharp quantitative stability estimates for the Brezis-Nirenberg problem

Abstract: We study the quantitative stability for the classical Brezis-Nirenberg problem associated with the critical Sobolev embedding $$H^1_0(\Omega) \hookrightarrow L<sup>{\frac{2n}{n-2}}(\Omega)$$ in a smooth bounded domain $\Omega \subset \mathbb{R}<sup>n$ ($n \geq 3$). To the best of our knowledge, this work presents the first quantitative stability result for the Sobolev inequality on bounded domains. A key discovery is the emergence of unexpected stability exponents in our estimates, which arise from the intricate interaction among the nonnegative solution $u_0$ and the linear term $\lambda u$ of the Brezis--Nirenberg equation, bubble formation, and the boundary effect of the domain $\Omega$. One of the main challenges is to capture the boundary effect quantitatively, a feature that fundamentally distinguishes our setting from the Euclidean case treated in \cite{CFM, FG, DSW} and the smooth closed manifold case studied in \cite{CK}. In addressing a variety of difficulties, our proof refines and streamlines several arguments from the existing literature while also resolving new analytical challenges specific to our setting.