MG15 - Talk detail

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The aim of this work is to argue that one can read off the pre-inflationary initial anisotropy of space from the angular distribution of primordial gravitational waves (PGWs). We take the Kasner-de Sitter spacetime as a model for inflation, consisting of a Kasner-like, Bianchi type-I anisotropic pre-inflationary stage and a succeeding isotropic inflationary stage driven by a cosmological constant. An apparent difficulty in calculating the PGWs of quantum origin in this setup arises from the fact that the Kasner spacetime with a general anisotropy has an initial singularity preventing us identifying the initial quantum state of the metric perturbations. However, since it is physically rather reasonable to expect that the early Kasner-like stage begins at a finite separation from the singularity, we try to construct the quantum states on the basis of adiabatically approximated modes evaluated at a finite initial time. The calculated quantum spectra of PGWs exhibit characteristic angular dependences reflecting the degree of the anisotropy, which we could use to explore the pre-inflationary initial state of the universe.

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