| 研究実績の概要 |
Our research during the first half year of JSPS tenure mainly 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 summarise our research achievements below:
We found that, in a class of massive gravity theories, the tensor perturbation originated from the vacuum fluctuations during inflation can be amplified substantially at the end of inflation. This gives rise to a possibility of generating large tensor perturbations in models of small field inflation in which they were regarded as completely unobservable.
Magnetic fields are present throughout the universe and play an important role in many astrophysical processes. However, its origin is still not well understood. On this issue, we proposed a mechanism to generate a large scale cosmic magnetic field from inflation. Our model is free from strong coupling and back reaction problems, which were two main obstacles in the literature of magnetic field genesis during early universe. Our model is a promising answer to this long standing puzzle of ubiquitous large scale cosmic magnetic fields.
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| 今後の研究の推進方策 |
The discovery of cosmic acceleration has completely changed our understanding of the universe. A possible explanation to this enigma is that gravity may be modified at cosmologically large distances. Several IR modified gravity models have interesting features in phenomena such as Integrated Sachs Wolfe (ISW) effect in CMB and baryon acoustic oscillations (BAO) in the large scale structure. We plan to investigate these observational effects in several modified gravity models, which include scalar tensor theories, massive gravity, DGP model, Horava-Lifshitz gravity, and Einstein-Gauss-Bonnet gravity.
Another mystery of the universe is the origin of matter asymmetry, that is, an excess of matter over antimatter. We plan to look for the possibility to produce this asymmetry in a modified theory of gravity beyond general relativity.
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