arXiv2026
This paper presents some qualitative properties of positive solutions to the strongly coupled system \[ \begin{cases} \displaystyle - Δu + τu = \frac{2 p}{p + q} \left( I_α\ast |v|^q \right) |u|^{p - 2} u &\text{in} ~ \mathbb{R}^N, \\ \\ \displaystyle - Δv + ηv = \frac{2 q}{p + q} \left( I_α\ast |u|^p \right) |v|^{q - 2} v &\text{in} ~ \mathbb{R}^N, \end{cases} \] with $τ, η> 0$, $N \in \mathbb{N}$, $0 < α< N$, \[ \max \left\{1, \frac{2 α}{N}\right\} < p, q < 2^* \quad \text{and} \quad \frac{2 (N + α)}{N} < p + q < 2_α^*, \] where $I_α$ denotes the Riesz potential, \[ 2^* := \begin{cases} \infty, &\text{if} ~ N \in \{1, 2\}, \\ \frac{2 N}{N - 2}, &\text{if} ~ N \geq 3, \end{cases} \quad \text{and} \quad 2_α^* := \begin{cases} \infty, &\text{if} ~ N \in \{1, 2\}, \\ \frac{2 (N + α)}{N - 2}, &\text{if} ~ N \geq 3. \end{cases} \] More precisely, by means of the moving planes method, we prove that positive solutions to this system are radially symmetric and strictly radially decreasing when $p, q \geq 2$, and we obtain a classification result for positive ground states in the case $p = q$ and $τ= η$.