论文标题
重力波镜头超出一般相对论：双折射，回声和阴影
Gravitational wave lensing beyond general relativity: birefringence, echoes and shadows
论文作者
论文摘要
引力波（GW）作为光，通过中间物质，偏转其轨迹，延迟其到达并偶尔产生多个图像来重力镜头。在一般相对论（GR）之外的理论中，新的引力自由度为GW镜头增添了额外的复杂性和丰富性。我们开发了一种形式主义，以计算GR在GR之外的GR繁殖，包括一般的空间时间，包括与新领域的动力学相互作用。我们的框架依赖于在短波扩展中识别领先顺序的动态传播特征状态（度量和其他字段的线性组合）。我们确定这些特征状态以及它们在镜头周围获得不同传播速度的条件。本征态之间的速度差异会导致双重现象，包括在没有电磁对应物的情况下观察到的度量极化之间的时间延迟（$ h _+，h_ \ times $）之间的时间延迟（$ h _+，h_ \ times $）。特别是，当累积的延迟大于信号持续时间时，会产生GW回声，而较短的时间延迟会产生波形形式的争夺。我们还将GW阴影的形成描述为非传播度量组件由镜头周围的其他字段的背景来源。例如，我们将我们的方法应用于具有Vainshtein筛选的四分之一的Horndeski理论，并表明双折射效应探测了参数空间的区域，以互补地互补，以互补，以互补的多通信器事件GW170817。将来，鉴定出强烈的GWS和二进制黑洞在密集的环境附近合并的二元黑洞（例如活跃的银河核）将满足这些新型重力测试的潜力。
Gravitational waves (GW), as light, are gravitationally lensed by intervening matter, deflecting their trajectories, delaying their arrival and occasionally producing multiple images. In theories beyond general relativity (GR), new gravitational degrees of freedom add an extra layer of complexity and richness to GW lensing. We develop a formalism to compute GW propagation beyond GR over general space-times, including kinetic interactions with new fields. Our framework relies on identifying the dynamical propagation eigenstates (linear combinations of the metric and additional fields) at leading order in a short-wave expansion. We determine these eigenstates and the conditions under which they acquire a different propagation speed around a lens. Differences in speed between eigenstates cause birefringence phenomena, including time delays between the metric polarizations (orthogonal superpositions of $h_+,h_\times$) observable without an electromagnetic counterpart. In particular, GW echoes are produced when the accumulated delay is larger than the signal's duration, while shorter time delays produce a scrambling of the wave-form. We also describe the formation of GW shadows as non-propagating metric components are sourced by the background of the additional fields around the lens. As an example, we apply our methodology to quartic Horndeski theories with Vainshtein screening and show that birefringence effects probe a region of the parameter space complementary to the constraints from the multi-messenger event GW170817. In the future, identified strongly lensed GWs and binary black holes merging near dense environments, such as active galactic nuclei, will fulfill the potential of these novel tests of gravity.
