HET Brown Bag Seminar | Log soft graviton theorem from BMS superrotation symmetry

In four spacetime dimensions, the soft graviton theorem exhibits a term that arises exclusively from one-loop diagrams and is logarithmic in the soft graviton energy. In this talk, we demonstrate that this term, known as the log soft graviton theorem, can be derived as the Ward identity of BMS superrotation symmetry, once long-range interactions are properly taken into account. We carry out a systematic analysis to all orders in the coupling and confirm that the log soft theorem is indeed one-loop exact.