发表机构
Universidad del País Vasco UPV/EHU（巴斯克大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
该研究探讨带任意符号宇宙学常数Λ的光子火箭（含点、弦、面源）的渐近引力辐射，基于渐近超坡印廷矢量等准则，明确不同Λ下辐射存在与否的判定条件，还关联了主零方向与辐射准则的几何关系。
AI 中文摘要
我们研究了具有一个类空 Killing 矢量和任意符号宇宙学常数Λ的纯辐射 Robinson-Trautman 度规在无穷远处引力辐射的存在性。这些度规描述了在时空中运动并发射零辐射的“光子火箭”，包括点源、弦源和面源。对于Λ≠0，我们基于渐近超坡印廷矢量的准则研究引力辐射的存在性。对于点源，我们将Λ=0时的已知结果推广到Λ≠0的情况，即 Kinnersley 火箭是唯一没有引力辐射的火箭。然而，对于弦源和面源，出现了新的无引力辐射的可能性。对于Λ>0，我们证明，相对于scri的单位法向量计算的正则渐近超坡印廷矢量的消失恰好表征了辐射的缺失。另一方面，对于Λ<0，我们证明，合适的准则是与scri相切的任意单位类时矢量相关的渐近超坡印廷矢量在scri法向分量的消失，或者等价地，Cotton-York 张量与scri处的全息应力张量成正比。特别地，我们提供了度规的具体例子，其中 Cotton-York 张量和全息应力张量可交换，但由于这两个张量不成比例，仍存在引力辐射。我们还确定了两种符号Λ下scri处重标 Weyl 张量的主零方向（PNDs），并将其相对于scri法向的几何结构与引力辐射的张量准则联系起来。
英文摘要
We study the existence of gravitational radiation at infinity for pure-radiation Robinson-Trautman metrics with one spacelike Killing vector and a cosmological constant $Λ$ of arbitrary sign. These metrics describe "photon rockets" with point, string, and sheet sources moving through spacetime while emitting null radiation. For $Λ\neq 0$, we use criteria for the existence of gravitational radiation based on the asymptotic super-Poynting vector. For point sources, we extend to $Λ\neq 0$ the known $Λ=0$ result that the Kinnersley rocket is the only rocket without gravitational radiation. However, for string and sheet sources, new possibilities without gravitational radiation arise. For $Λ>0$, we show that the vanishing of the canonical asymptotic super-Poynting vector---computed with respect to the unit normal to scri---exactly characterizes the absence of radiation. On the other hand, for $Λ<0$, we show that the appropriate criterion is the vanishing of the components normal to scri of the asymptotic super-Poynting vectors associated with any unit timelike vector tangent to scri or, equivalently, the proportionality between the Cotton-York tensor and the holographic stress tensor at scri. In particular, we provide explicit examples of metrics for which the Cotton-York and holographic stress tensors commute, yet gravitational radiation is present because the two tensors are not proportional. We also determine the principal null directions (PNDs) of the rescaled Weyl tensor at scri for both signs of $Λ$ and relate their geometry relative to the normal to scri to the tensorial criteria for gravitational radiation.
Comments16 pages, no figures
