Maximizers for the Singular Trudinger-Moser functional beyond the critical regime

Abstract

Our aim is to investigate the existence of local maximizers for the singular Trudinger-Moser functional $$ F_α(u) := \int_Ω \frac{e^{αu^2}-1}{|x|^{a}} \mathrm{d}x,\;\;\; u \in W_0^{1,2}(Ω), $$ restricted to the manifold $ Σ=:\left\{u\in W_0^{1,2}(Ω):\|\nabla u\|_2=1\right\},$ where $a\in [0, 2)$, $α\ge 0$ and $Ω$ denotes a smooth bounded domain $\mathbb{R}^2$ containing the origin. Adimurthi and Sandeep (Nonlinear. Differ. Equ. Appl. \textbf{13}, 2007) showed the following singular Trudinger-Moser type estimate \begin{equation}\nonumber \sup_{u \in W_0^{1,2}(Ω), \, \|\nabla u\|_{L^2} \le 1} F_α(u)<\infty\;\;\;\mbox{iff}\;\;α\leq α_a:=2π(2-a). \end{equation} In particular, the functional $F_α$ is bounded on $ Σ$ whenever $α\le α_a$. In addition, Csató and Roy (Calc. Var. Partial Differ. Equ., \textbf{54}, 2015) were able to ensure the existence of maximizers for $F_α$ on $Σ$ when $α\le α_a$. In the supercritical regime $α> α_a$, the functional $F_α$ becomes unbounded on $Σ$. Nevertheless, we prove that $F_α$ still possesses local maximizers on $Σ$ beyond the critical threshold, at least for $α> α_a$ sufficiently close to $α_a$. Our approach relies on a variational analysis near the set of maximizers associated with the critical parameter $α_a$, together with a suitable local compactness argument. Our result improves and complements related findings due to Struwe (Ann. Inst. Henri Poincaré, Anal. Non Linéaire, \textbf{5}, 1988).