| 研究実績の概要 |
Our research in FY2016 focused on searching new physics in cosmology. We have been working on the theories beyond general relativity and standard model in particle physics during very early universe.
We performed the Hamiltonian analysis of an on-shell U(1) gauge field theory, in which the action is not invariant under local U(1) transformations but recovers the invariance when the equations of motion are imposed. We found that the photons have only two polarisations, although the standard U(1) symmetry is explicitly broken. The results are confirmed by an independent analysis based on the Faddeev-Jackiw Hamiltonian reduction approach. The modified U(1) gauge field theory has very interesting applications on the primordial magnetogenesis.
1.We considered a cosmological model in which the tensor mode becomes massive during inflation, and study the Cosmic Microwave Background (CMB) temperature and polarization bispectra arising from the mixing between the scalar mode and the massive tensor mode during inflation. The model assumes the existence of a preferred spatial frame during inflation. The local Lorentz invariance is already broken in cosmology due to the existence of a preferred rest frame. The existence of a preferred spatial frame further breaks the remaining local SO(3) invariance and in particular gives rise to a mass in the tensor mode. Very intriguingly, we find a surprising similarity between the predicted scale dependence and the scale-dependent non-Gaussianities at low multipoles hinted in the WMAP and Planck results.
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