Dynamics of the Energy-Critical Nonlinear Schrödinger System in ${\mathbb R}^{4}$
Alex H. Ardila
TL;DR
This work analyzes the energy-critical, three-component nonlinear Schrödinger system in $\mathbb{R}^4$ at the ground-state energy, focusing on radial threshold dynamics under the mass-resonance condition $2m_1+m_2=m_3$. A key novelty is the two-dimensional kernel of the imaginary part of the linearized operator, which necessitates a refined modulation scheme with two phase parameters and a coercivity analysis of the linearized system. The authors construct two distinguished threshold solutions $\mathcal{G}^{\pm}$ and develop a comprehensive spectral-modulation framework to obtain a full classification of threshold dynamics: global existence, scattering, convergence to ground-state or to the special threshold profiles, and finite-time blow-up. Central to the approach are virial identities, precise modulation near the ground state $\mathcal{Q}$, and a detailed spectral theory of the linearized operator $\mathcal{L}$, including the existence of a negative eigenvalue and the characterization of neutral directions. The results extend the understanding of energy-critical multi-component NLS dynamics beyond the scalar case, highlighting the role of multi-parameter modulation and two-dimensional kernel effects in threshold phenomena.
Abstract
In this paper, we investigate the dynamics of radial solutions at threshold energy for a 3-component Schrödinger system with cubic nonlinearity in four dimensions. The main difference from the cases previously addressed in the literature is that, in our system, the kernel of the imaginary part $L_I$ of the linearized operator $-i{\mathcal L}=L_{R}+iL_{I}$ has dimension 2. To overcome this difficulty, we carry out a detailed study of the coercivity properties of these operators. We also introduce a new modulation parameter associated with the additional eigenfunction in the kernel of the operator $L_{I}$, which enables us to perform the modulation analysis and establish the uniqueness of exponentially decaying solutions to the linearized equation.
