On $p$-fractional weakly-coupled system with critical nonlinearities
Nirjan Biswas, Souptik Chakraborty
TL;DR
The paper analyzes a $p$-fractional weakly-coupled system with critical nonlinearities on $\mathbb{R}^d$ driven by the operator $(-\Delta_p)^s$ with $0<s<1$, $d>sp$, and $\alpha+\beta=p_s^*$. It develops a global compactness framework by providing a full Palais–Smale decomposition of the associated energy functional $I_{f,g}$, revealing how PS sequences can split into a weak limit solving the full system plus a finite number of homogeneous bubbles, with precise energy and mutual-orthogonality properties. Leveraging this decomposition, the authors prove the existence of a positive, negative-energy solution when $\ker(f)=\ker(g)$ (for a restricted range of $s$), and they derive conditions under which the two components are distinct. The results advance the theory of nonlocal coupled systems at critical growth and give a robust variational toolkit for non-homogeneous fractional $p$-Laplacian systems on $\mathbb{R}^d$.
Abstract
This paper deals with the following nonlocal system of equations: \begin{align}\tag{$\mathcal S$}\label{MAT1} (-Δ_p)^s u = \fracα{p_s^*}|u|^{α-2}u|v|^β+f(x) \text{ in } \mathbb{R}^{d}, \, (-Δ_p)^s v = \fracβ{p_s^*}|v|^{β-2}v|u|^α+g(x) \text{ in } \mathbb{R}^{d},\; u,v >0 \mbox{ in } \mathbb{R}^{d}, \end{align} where $0<s<1<p< \infty$, $d>sp$, $α,β>1$, $α+β=\frac{dp}{d-sp}$, and $f,g$ are nontrivial nonnegative functionals in the dual space of $\mathcal{D}^{s,p}(\mathbb{R}^{d})$. The primary objective of this paper is to present a global compactness result that offers a complete characterization of the Palais-Smale sequences of the energy functional associated with \eqref{MAT1}. Using this characterization, within a certain range of $s$, we establish the existence of a solution with negative energy for \eqref{MAT1} when $\ker(f)=\ker(g)$.
