Local well-posedness for Chern-Simons gauged $O(3)$ sigma equations under the Lorenz gauge
Jin Guanghui, Huali Zhang
TL;DR
This paper establishes local well-posedness for the Chern-Simons gauged $O(3)$ sigma model under the Lorenz gauge in two spatial dimensions for data near the energy-critical regularity of the matter field. The authors exploit the hidden null-form structure in the nonlinearities and develop bilinear estimates in wave-Sobolev spaces $H^{s,b}$ to control the dynamics, together with a decomposition of the gauge field into divergence-free and curl-free components. The main result shows existence, uniqueness, and continuous dependence for initial data in $H^{s}(\mathbb{R}^2) \times H^{s-\frac12}(\mathbb{R}^2)$ with $s>1$, along with precise regularity for the gauge field in $H^{s-\frac12}$ and $H^{s-\frac32}$ for the temporal derivative. An energy-conservation identity is provided in the appendix, anchoring the local theory to the model's physical invariants. Overall, the work advances low-regularity well-posedness for gauge-coupled nonlinear sigma models and highlights the role of null structure in such systems.
Abstract
In this paper, we study the Cauchy problem for the Chern-Simons gauged $O(3)$ sigma model under the Lorenz gauge condition. We prove the local well-posedness of solutions if the initial matter field and gauge field satisfy $(\bmφ_0, \bA_0) \in H^s(\R^2)\times H^{s-\frac12}(\R^2)$, $s>1$, where the critical regularity for $\bmφ_0$ is $s_c=1$. Our proof is based on identifying null forms within the system and utilizing bilinear estimates in wave-Sobolev space.
