Segregated solutions for nonlinear Schrödinger systems with sublinear coupling terms
Qing Guo, Chengxiang Zhang
Abstract
We establish the existence of infinitely many nonnegative, segregated solutions for the sublinearly coupled Schrödinger system \begin{equation*} \left\{\begin{aligned}-Δu+K_1(x)u&=μu^{p-1}+ (σ_1+1)βu^{σ_1}v^{σ_2+1}, &x\in\mathbb{R}^N&, -Δv+K_2(x)v&=νv^{p-1}+(σ_2+1)βu^{σ_1+1}v^{σ_2}, &x\in\mathbb{R}^N&,\end{aligned}\right. \end{equation*}where $N \geq 2$, $p \in (2,2^*)$, $2^* = 2N/(N-2)$ ($2^* = \infty$ if $N=2$), $K_j$ are radial potentials, $μ, ν> 0$, $β\in \mathbb{R}$, and critically $σ_j \in (0,1)$. The sublinear coupling exponents $σ_j$ introduce fundamental challenges due to nonsmooth nonlinearities and singularities in standard reduction methods. To overcome this, we develop an enhanced Lyapunov-Schmidt reduction framework. By recasting the problem within a specially constructed metric space of local minimizers for an outer boundary value problem, we derive sharp a priori estimates enabling contraction mapping arguments. This approach circumvents the limitations of classical methods for sublinear couplings. We further uncover a novel "dead core" phenomenon: solutions $(u_\ell, v_\ell)$ exhibit non-strict positivity with topological segregation. Specially, for $N=2$ and large integers $\ell$, there exist radii $0 < R_1 < R_2$ such that $\text{supp } u_\ell \subset B_{R_2}(0)$, $\text{supp } v_\ell \subset \mathbb{R}^N \setminus B_{R_1}(0)$, and $u_\ell + v_\ell \to 0$ uniformly in $B_{R_2}(0) \setminus B_{R_1}(0)$ as $\ell \to \infty$. Our methodology provides a versatile framework for handling nonsmooth nonlinearities in reduction techniques.