We study the caustics on the boundaries of entanglement wedges in the context of holography in asymptotically AdS 3 spacetimes. These entanglement wedges play an important role in our understanding of the emergence of bulk locality. A procedure was proposed by Sanches and Weinberg for identifying boundary operators which are local in the bulk, which also applies to certain regions that lie beyond the reach of HRT surfaces by taking advantage of the lightsheets which bound entanglement wedges. We identify the caustics which terminate these lightsheets in conical deficit and BTZ black hole spacetimes and find that in some examples these caustics lead to a sharp corner in the entanglement wedge. The unexpected shape of these entanglement wedges leads, in those cases, to a breakdown of this procedure. Many of the properties of the rich variety of caustics possible in higher dimensions remains to be explored which, as this work demonstrates, could lead to more unexpected features in the shapes of entanglement wedges.

中文翻译：

---

焦散边界纠缠楔形

我们研究了渐近 AdS 3 时空全息背景下纠缠楔边界上的焦散。这些纠缠楔在我们理解体局域性的出现中发挥着重要作用。Sanches 和 Weinberg 提出了一种程序，用于识别体中局部的边界算子，该程序也适用于通过利用绑定纠缠楔的光片而超出 HRT 表面范围的某些区域。我们确定了在锥形赤字和 BTZ 黑洞时空中终止这些光片的焦散，并发现在某些示例中，这些焦散导致纠缠楔中的尖角。在这些情况下，这些纠缠楔的意外形状会导致此过程中断。