Critical fractional Kirchhoff problems: Uniqueness and Nondegeneracy
Zhipeng Yang, Yuanyang Yu
TL;DR
This work studies a critical fractional Kirchhoff equation on $\mathbb{R}^N$ with a nonlocal coefficient depending on the gradient energy. It proves the uniqueness of the positive ground state up to translation and a full nondegeneracy property of the linearized operator, by relating the Kirchhoff problem to the standard fractional critical problem through a scaling parameter and exploiting the bubble profile for $(-\Delta)^s u = u^{2^*_s-1}$. The key contributions are a scaling-based uniqueness reduction and a complete angular-momentum–decomposed nondegeneracy analysis, which underpin singular perturbation methods for fractional Kirchhoff models and extend known results to the critical, high-dimensional fractional setting. These results enhance understanding of the qualitative behavior and stability of ground states in nonlocal nonlinear PDEs and provide a framework for further perturbation studies.
Abstract
In this paper, we consider the following critical fractional Kirchhoff equation \begin{equation*} \Big(a+b{\int_{\mathbb{R}^{N}}}|(-Δ)^{\frac{s}{2}}u|^2dx\Big)(-Δ)^su=|u|^{2^*_s-2}u,\quad \text{in}\ \mathbb{R}^{N}, \end{equation*} where $a,b>0$, $\frac{N}{4}<s<1$, $2^*_s=\frac{2N}{N-2s}$ and $(-Δ)^s$ is the fractional Laplacian. We prove the uniqueness and nondegeneracy of positive solutions to the problem, which can be used to study the singular perturbation problems concerning fractional Kirchhoff equations.
