2016 Fiscal Year Annual Research Report
Modified gravity and its cosmology
| Project/Area Number |
15F15321
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| Research Institution | Kyoto University |
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Principal Investigator |
佐々木 節 京都大学, 基礎物理学研究所, 教授 (70162386)
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| Co-Investigator(Kenkyū-buntansha) |
LIN CHUNSHAN 京都大学, 基礎物理学研究所, 外国人特別研究員
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| Project Period (FY) |
2015-11-09 – 2018-03-31
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| Keywords | 修正重力理論 / 宇宙論的重力波 / 非ガウス揺らぎ |
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| Outline of Annual Research Achievements |
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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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
新たなアイデアに基づいた理論の構築も進んでおり，論文発表も順調に進んでいる。
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| Strategy for Future Research Activity |
これまで通りに，新たなアイデアを取り入れつつ，着実に研究を進める。
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Research Products
(2 results)
