New Insights into Primordial Gravitational Waves from Inflationary Models

Recent research by Takahiro Tanaka and Yuko Urakawa, titled "Statistical anisotropy of primordial gravitational waves from generalized δN formalism," explores the behavior of primordial gravitational waves in the context of cosmic inflation. The authors utilize a generalized δN formalism to analyze large-scale fluctuations, including gravitational waves, by solving the evolution of the background homogeneous Universe. They derive an analytic formula that connects fluctuations at the horizon crossing with the gravitational waves produced at the end of inflation. This formula can also be applied to inflation models featuring anisotropic backgrounds.

The study discusses conditions under which linear polarization of gravitational waves can occur and highlights differences between single- and multi-gauge field models. These findings could have significant implications for understanding the early Universe and the nature of gravitational waves, potentially influencing future observational strategies in cosmology.

The paper is available for reference at arXiv:2309.08497.