标题： Lovelock理论中的激波形成 显示英文标题

标题： Shock Formation in Lovelock Theories

摘要： 我们认为，与广义相对论不同，Lovelock 引力理论存在冲击形成的问题。 我们考虑了（i）曲率中的间断性传播，以及（ii）弱高频引力波的传播。 这类扰动沿“背景”时空的特征超曲面传播，其振幅由一个输运方程控制。 在广义相对论中，输运方程是线性的。 在Lovelock理论中，它是非线性的，其解可能会发散，对应于冲击的形成。 我们证明了这种效应在某些简单情况下（例如平坦背景时空）不存在，并展示了它在平面波背景下的存在。 我们讨论了弱宇宙监督、冲击的演化以及在Lovelock理论中闵可夫斯基时空的非线性稳定性。 显示英文摘要

摘要： We argue that Lovelock theories of gravity suffer from shock formation, unlike General Relativity. We consider the propagation of (i) a discontinuity in curvature, and (ii) weak, high frequency, gravitational waves. Such disturbances propagate along characteristic hypersurfaces of a "background" spacetime and their amplitude is governed by a transport equation. In GR the transport equation is linear. In Lovelock theories, it is nonlinear and its solutions can blow up, corresponding to the formation of a shock. We show that this effect is absent in some simple cases e.g. a flat background spacetime, and demonstrate its presence for a plane wave background. We comment on weak cosmic censorship, the evolution of shocks, and the nonlinear stability of Minkowski spacetime, in Lovelock theories.