A central feature of scattering amplitudes in gravity or gauge theory is the existence of a variety of energetically soft theorems which put constraints on the amplitudes. Celestial amplitudes which are obtained from momentum-space amplitudes by a Mellin transform over the external particle energies cannot obey the usual energetically soft theorems. Instead, the symmetries of the celestial sphere imply that the scattering of conformally soft particles whose conformal weights under the 4D Lorentz group SL(2,C) are taken to zero obey special relations. Such conformally soft theorems have recently been found for gauge theory. Here, I show conformally soft factorization of celestial amplitudes for gravity and identify it as the celestial analogue of Weinberg's soft graviton theorem.

中文翻译：

---

引力中的共形软定理

引力或规范理论中散射振幅的一个中心特征是存在各种对振幅施加约束的能量软定理。通过外部粒子能量的梅林变换从动量空间振幅获得的天体振幅不能遵守通常的能量软定理。相反，天球的对称性意味着在 4D 洛伦兹群 SL(2,C) 下的共形权重为零的共形软粒子的散射服从特殊关系。最近在规范理论中发现了这种共形软定理。在这里，我展示了引力天体振幅的共形软分解，并将其识别为 Weinberg 软引力子定理的天体类似物。