Integrable Systems and Harmonic Maps into Lie Groups

Regularity for solutions of H-systems and n-harmonic maps with n/2 square integrable derivatives

We study the regularity of weak solutions for two elliptic systems involving the $n$-Laplacian and a critical nonlinearity in the right hand side: $H$-systems and $n$-harmonic maps into compact Riemannian manifolds. Under the assumptions that the solutions belong to $W^{n/2,2}$ in an even dimension $n$, we prove their continuty. The tools used in the proof involve Hardy spaces and BMO, and the Rivière--Uhlenbeck decomposition (with estimates in Morrey spaces). A prominent role is played by the Coifman--Rochberg--Weiss commutator theorem.

Biharmonic maps into compact Lie groups and the integrable systems

The reduction of biharmonic maps equation in terms of the Maurer-Cartan form for all smooth map of any compact Riemannian manifolds into a compact Lie group with bi-invariant Riemannian metric is obtained. By this formula, all the biharmonic curves into a compact Lie group and all biharmonic maps from a 2-dimensional open domain into a compact Lie group are characterized.

Groupoids and the integration of Lie algebroids

We show that a Lie algebroid on a stratified manifold is integrable if, and only if, its restriction to each strata is integrable. These results allow us to construct a large class of algebras of pseudodifferential operators.

次黎曼李群的调和态射

Harmonic morphisms of sub-Riemannian Lie groups

本文证明次黎曼李群间的调和态射是光滑共形淹没且为拉普拉斯算子的对称性，给出李群外调和态射的部分结果，计算其水平能量第一变分，发现其不一定是调和映射。