超平移是软规范

中文摘要 AI 辅助

由于质量间隙的缺失，电动力学和引力中大量粒子的渐近态无法被唯一确定。我们在KMOC形式体系下，研究了这种自由度对大量粒子态的规范修饰所带来的经典含义。我们证明，相干态修饰会通过大规范/BMS变换修改可观测量。相关的相干态位移算符可被补充为一个守恒电荷，在引力情形下即BMS电荷，该电荷对散射数据实施大规范变换。我们的修饰参数直接就是大规范/BMS变换参数，且我们证明，可观测量在所有阶上都不依赖于变换参数的单极和偶极部分。我们的构造由软因子化驱动，而非由底层的局域对称性驱动，我们通过在一种无规范对称性的标量理论中展示相同结构来说明这一点。我们探究了大规范变换对两粒子态的作用，涉及标量、阿贝尔规范和引力子媒介三种情形，得到了碰撞参数的普适偏移，并阐明了辐射角动量相对于总角动量的框架独立性所具有的框架依赖性。连接正则BMS框架（其中施瓦西度规取克尔-席尔德形式）与固有框架（其中度规取德东纳形式）的变换具体例证了这些效应。

英文摘要

Asymptotic states of massive particles in electrodynamics and gravity are not uniquely defined because of the absence of a mass gap. Working in the KMOC formalism, we study the classical implications of this freedom in the dressing of massive particle states. We show that coherent-state dressings modify observables by a large gauge/BMS transformation. The associated coherent-state displacement operator can be completed into a conserved charge, the BMS charge in the gravitational case, which implements large gauge transformations on scattering data. The parameter of our dressing is directly the large gauge/BMS transformation parameter, and we explain that observables do not depend on monopolar and dipolar parts of the transformation parameter to all orders. Our construction is driven by soft factorization rather than by an underlying local symmetry, and we illustrate this by exhibiting the same structure in a scalar theory with no gauge symmetry. We explore the action of large gauge transformations on two-particle states for scalar, abelian gauge and graviton mediators, obtaining a universal shift of the impact parameter and clarifying the frame dependence of the radiated angular momentum vis à vis the frame-independence of the total angular momentum. The transformation connecting the canonical BMS frame, in which the Schwarzschild metric takes the Kerr-Schild form, to the intrinsic frame, in which it takes the De Donder form, illustrates these effects concretely.

补充信息

备注

58 pages, 2 figures