Namikawa Toshiya, Sherwin Blake D
Center for Data-Driven Discovery, Kavli Institute for the Physics and Mathematics of the Universe (WPI), UTIAS, The University of Tokyo, Kashiwa 277-8583, Japan.
Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Wilberforce Road, Cambridge CB3 0WA, United Kingdom and Kavli Institute for Cosmology, University of Cambridge, Madingley Road, Cambridge CB3 OHA, United Kingdom.
Phys Rev Lett. 2023 Sep 29;131(13):131001. doi: 10.1103/PhysRevLett.131.131001.
We propose a new probe of inflationary gravitational waves (IGWs): the cross-correlation of the lensing of inflationary B-mode polarization with a large-scale structure (LSS) tracer, which can also be a cosmic microwave background (CMB) lensing map. This is equivalent to measuring a three-point function of two CMB B-modes and an LSS tracer. We forecast expected 1σ constraints on the tensor-to-scalar ratio r, albeit with a simplistic foreground treatment, and find constraints of σ_{r}≃7×10^{-3} from the correlation of CMB-S4-Deep B-mode lensing and LSST galaxies, σ_{r}≃5×10^{-3} from the correlation of CMB-S4-Deep B-mode lensing and CMB-S4-Deep CMB lensing, and σ_{r}≃10^{-2} from the correlation of LiteBIRD B-mode lensing and CMB-S4-Wide lensing. Because this probe is inherently non-Gaussian, simple Gaussian foregrounds will not produce any biases to the measurement of r. While a detailed investigation of non-Gaussian foreground contamination for different cross-correlations will be essential, this observable has the potential to be a useful probe of IGWs, which, due to different sensitivity to many potential sources of systematic errors, can be complementary to standard methods for constraining r.
我们提出了一种新的暴胀引力波（IGWs）探测方法：暴胀B模式偏振的引力透镜效应与大尺度结构（LSS）示踪剂的交叉相关性，该示踪剂也可以是宇宙微波背景（CMB）引力透镜图。这等同于测量两个CMB B模式和一个LSS示踪剂的三点函数。我们预测了对张量与标量比r的预期1σ约束，尽管采用了简单的前景处理方法，并发现CMB-S4-Deep B模式引力透镜与LSST星系的相关性给出的约束为σ_{r}≃7×10^{-3}，CMB-S4-Deep B模式引力透镜与CMB-S4-Deep CMB引力透镜的相关性给出的约束为σ_{r}≃5×10^{-3}，LiteBIRD B模式引力透镜与CMB-S4-Wide引力透镜的相关性给出的约束为σ_{r}≃10^{-2}。由于这种探测本质上是非高斯的，简单的高斯前景不会对r的测量产生任何偏差。虽然对不同交叉相关性的非高斯前景污染进行详细研究至关重要，但这种可观测性有可能成为IGWs的有用探测方法，由于对许多潜在系统误差源具有不同的敏感性，它可以补充用于约束r的标准方法。
