Global bifurcations of nodal solutions for coupled elliptic equations
Haoyu Li, Olímpio Hiroshi Miyagaki, Zhi-Qiang Wang
TL;DR
This work analyzes the global bifurcation structure of radial nodal solutions to a three-dimensional coupled cubic elliptic system on the unit ball, using the coupling constant $\beta$ as the bifurcation parameter. It identifies four synchronized and four semi-trivial branches for each nodal level $k$ and proves the existence of infinitely many global bifurcating branches from eight base curves, with distinct structures for different $k$. The approach combines a weighted eigenvalue problem, Morse-index calculations, Rabinowitz-type global bifurcation, and Liouville-type nonexistence theorems, complemented by careful nodal analysis and asymptotics as $\beta\to\infty$. The results yield a fairly complete nodal classification of the coupled system, reveal how coupling affects nodal patterns, and enable applications such as comparing scalar nodal solutions and refining nonexistence thresholds near $\beta=3$. Overall, the paper advances understanding of interspecies coupling effects in radial nodal solutions of coupled elliptic systems and provides a robust framework for analyzing similar problems.
Abstract
We investigate the global bifurcation structure of the radial nodal solutions to the coupled elliptic equations \begin{equation} \left\{ \begin{array}{lr} -Δu+u=u^3+βuv^2\mbox{ in }B_1 ,\nonumber -Δv+v=v^3+βu^2v\mbox{ in }B_1 ,\nonumber u,v\in H_{0,r}^1(B_1).\nonumber \end{array} \right. \end{equation} Here $B_1$ is a unit ball in $\mathbb{R}^3$ and $β\in\mathbb{R}$ the coupling constant is used as bifurcation parameter. For each $k$, the unique pair of nodal solutions $\pm w_k$ with exactly $k-1$ zeroes to the scalar field equation $-Δw + w=w^3$ generate exactly four synchronized solution curves and exactly four semi-trivial solution curves to the above system. We obtain a fairly complete global bifurcation structure of all bifurcating branches emanating from these eight solution curves of the system, and show that for different $k$ these bifurcation structures are disjoint. We obtain exact and distinct nodal information for each of the bifurcating branches, thus providing a fairly complete characterization of nodal solutions of the system in terms of the coupling.
