There has been considerable progress in recent years in solving inverse problems for nonlinear hyperbolic equations. One of the striking aspects of these developments is the use of nonlinearity to get new information, which is not possible for the corresponding linear equations. We illustrate this for several examples including Einstein equations and the equations of nonlinear elasticity among others.

中文翻译：

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非线性双曲方程的反问题

近年来，在解决非线性双曲型方程的反问题方面取得了长足的进步。这些发展的显着方面之一是利用非线性获得新信息，这对于相应的线性方程式是不可能的。我们通过几个示例对此进行说明，其中包括爱因斯坦方程和非线性弹性方程。