论文标题
重力散射，辐射反应和Bondi量规歧义的角动量丧失
Angular momentum loss in gravitational scattering, radiation reaction, and the Bondi gauge ambiguity
论文作者
论文摘要
最近，达莫尔（Damour）计算了重力散射的辐射反应，因为他发现重力常数中对角动量损失的（线性）反应，他发现该反应为$ {\ cal o}（g^2）$。这是一个难题，因为任何振幅计算都会产生能量和角动量损失，仅在$ {\ cal o}（g^3）$开始。另一个难题是，$ {\ cal o}（g^3）$的结果辐射反应是正确的，并通过许多直接计算确认。我们将这些难题归因于BMS的歧义，以定义角动量。角动量的丧失应从ADM值中计算出来，因此应在BMS转换下的所谓规范仪表中计算，其中Bondi角动量的远程PAST限制与ADM角动量重合。该计算正确地给出了$ {\ cal o}（g^3）$损失。另一方面，我们引入了一个量规，其中邦迪光锥体渐近地倾向于从大众世界线中心散发出来的尺寸。我们发现该仪表中的角动量通量恰恰是Damour用于其辐射反应结果的一种。我们称该新的量规为“内在”，并认为尽管要在规范仪表中计算正确的角动量通量，但任何机械计算量规依赖量的机械计算（例如角动量）为内在仪表提供了结果。因此，正是该量规应在线性响应公式中使用。这解决了难题，并建立了内在的机械计算与邦迪形式主义之间的对应关系。
Recently, Damour computed the radiation reaction on gravitational scattering as the (linear) response to the angular momentum loss which he found to be of ${\cal O}(G^2)$ in the gravitational constant. This is a puzzle because any amplitude calculation would produce both energy and angular momentum losses starting only at ${\cal O}(G^3)$. Another puzzle is that the resultant radiation reaction, of ${\cal O}(G^3)$, is nevertheless correct and confirmed by a number of direct calculations. We ascribe these puzzles to the BMS ambiguity in defining angular momentum. The loss of angular momentum is to be counted out from the ADM value and, therefore, should be calculated in the so-called canonical gauge under the BMS transformations in which the remote-past limit of the Bondi angular momentum coincides with the ADM angular momentum. This calculation correctly gives the ${\cal O}(G^3)$ loss. On the other hand, we introduce a gauge in which the Bondi light cones tend asymptotically to those emanating from the center of mass world line. We find that the angular momentum flux in this gauge is precisely the one used by Damour for his radiation reaction result. We call this new gauge "intrinsic" and argue that, although the correct angular momentum flux is to be computed in the canonical gauge, any mechanical calculation of gauge-dependent quantities -- such as angular momentum -- gives the result in the intrinsic gauge. Therefore, it is this gauge that should be used in the linear response formula. This solves the puzzles and establishes the correspondence between the intrinsic mechanical calculations and the Bondi formalism.
