标题： 紫外/红外对应的一些方面：能量展宽和弦波动 显示英文标题

标题： Aspects of the UV/IR correspondence : energy broadening and string fluctuations

摘要： 我们证明，一个在强耦合N=4 SYM理论的真空中辐射的源会产生一个能量分布，在超引力近似下，其时空模式与相应的经典分布相同：辐射以光速传播而不扩展。 我们通过几个例子来说明这一点：一个沿稳定弦向下传播的小扰动，一个无质量粒子落入AdS_5，以及一个类时波包的衰变。 在Phys. Rev. D81 (2010) 126001中，对于旋转弦的情况也做出了类似的观察。 在所有这些情况下，没有扩展的现象是由于边界上的能量反作用仅来自靠近边界的体区扰动。 这是因为以光速在AdS_5中传播的体源不会在边界上产生任何能量。 我们将这些特征解释为超引力近似的产物，该近似未能包含即使在强耦合极限下也应该存在的量子力学涨落。 我们认为，这样的涨落应该作为纵向弦涨落进入对偶弦理论，在强耦合下不会被抑制。 我们粗略地估计了这些涨落的影响，并认为它们会恢复辐射的扩展，这与量子力学和紫外/红外对应性的预期一致。 显示英文摘要

摘要： We show that a source which radiates in the vacuum of the strongly coupled N=4 SYM theory produces an energy distribution which, in the supergravity approximation, has the same space-time pattern as the corresponding classical distribution: the radiation propagates at the speed of light without broadening. We illustrate this on the basis of several examples: a small perturbation propagating down a steady string, a massless particle falling into AdS_5, and the decay of a time-like wave-packet. A similar observation was made in Phys. Rev. D81 (2010) 126001 for the case of a rotating string. In all these cases, the absence of broadening is related to the fact that the energy backreaction on the boundary arises exclusively from the bulk perturbation at, or near, the boundary. This is so since bulk sources which propagate in AdS_5 at the speed of light do not generate any energy on the boundary. We interpret these features as an artifact of the supergravity approximation, which fails to encode quantum mechanical fluctuations that should be present even in the strong coupling limit. We argue that such fluctuations should enter the dual string theory as longitudinal string fluctuations, which are not suppressed at strong coupling. We heuristically estimate the effects of such fluctuations and argue that they restore the broadening of the radiation, in agreement with expectations from both quantum mechanics and the ultraviolet/infrared correspondence.