标题： 二维目标空间上可积孤子模型的特征分析 显示英文标题

标题： Characteristic analysis for integrable soliton models on two-dimensional target spaces

摘要： 我们研究了一些可积孤立子模型的进化特性，这些模型的拉格朗日量是从体积形式在二维目标空间上的拉回到的。 这些模型已知具有无限多的守恒量，并支持各种具有非平凡拓扑的精确解析解。 特别是，我们证明了尽管它们允许良好的光滑解，但关于这些解的波传播总是不适定的。 这与相应的欧拉-拉格朗日方程不是双曲型有关。 显示英文摘要

摘要： We investigate the evolutionary aspects of some integrable soliton models whose Lagrangians are derived from the pullback of a volume-form to a two-dimensional target space. These models are known to have infinitely many conserved quantities and support various types of exact analytic solutions with nontrivial topology. In particular, we show that, in spite of the fact that they admit nice smooth solutions, wave propagation about these solutions will always be ill-posed. This is related to the fact that the corresponding Euler-Lagrange equations are not of hyperbolic type.