School of Physics and Astronomy, University of Nottingham, University Park, Nottingham NG7 2RD, United Kingdom.
Department of Physics, Simon Fraser University, Burnaby, British Colombia V5A 1S6, Canada.
Phys Rev Lett. 2014 May 2;112(17):171302. doi: 10.1103/PhysRevLett.112.171302. Epub 2014 Apr 29.
Scaling networks of cosmic defects, such as strings and textures, actively generate scalar, vector, and tensor metric perturbations throughout the history of the Universe. In particular, vector modes sourced by defects are an efficient source of the cosmic microwave background B-mode polarization. We use the recently released BICEP2 and POLARBEAR B-mode polarization spectra to constrain properties of a wide range of different types of cosmic strings networks. We find that in order for strings to provide a satisfactory fit on their own, the effective interstring distance needs to be extremely large--spectra that fit the data best are more representative of global strings and textures. When a local string contribution is considered together with the inflationary B-mode spectrum, the fit is improved. We discuss implications of these results for theories that predict cosmic defects.
宇宙缺陷（如弦和纹理）的网络扩展会在宇宙的历史中积极地产生标量、矢量和张量度规扰动。特别是由缺陷引起的矢量模式是宇宙微波背景 B 模式极化的有效源。我们利用最近发布的 BICEP2 和 POLARBEAR B 模式极化谱来约束各种不同类型的宇宙弦网络的性质。我们发现，为了使弦自身提供令人满意的拟合，有效弦之间的距离需要非常大——最能拟合数据的谱更能代表全局弦和纹理。当将局部弦贡献与通货膨胀 B 模式谱一起考虑时，拟合得到了改善。我们讨论了这些结果对预测宇宙缺陷的理论的意义。
