表題番号：2020C-774
日付：2021/04/02

研究課題Cosmological dynamics and screening mechanisms of modified gravity theories

研究者所属（当時） | 資格 | 氏名 | |
---|---|---|---|

（代表者） | 理工学術院 先進理工学部 | 講師 | パンパーニッチ シラチャック |

（連携研究者） | Waseda University | Professor | MAEDA Kei-ichi |

- 研究成果概要
- We study cosmology dynamics of the cuscuta-galileon gravity. This model has only two gravitational degrees of freedom as the General Relativity, thus it is satisfied observations in the solar system scale. We use dynamical system approach to find behavior under cosmological background. We found that the cuscuta-galileon model without a potential term cannot provide the thermal history of the universe correctly. After adding a potential term we successfully find radiation dominated, matter dominated, and dark energy dominated eras. By studying stabilities of the dynamical system we found that if we start from the radiation dominated era, it will follow by matter dominated and dark energy dominated eras respectively which corresponds to the thermal history of the universe. Therefore the model can be one of the candidates for the dark energy to explain the accelerated expansion of the universe. However, the amount of dark energy in the matter dominated and the radiation dominated eras is large comparing to the cosmological constant. Thus, some observations such as the Cosmic Microwave Background, the cuscuta-galileon gravity may not satisfy. Moreover, in the perturbations level we found that there is an instability in the model which arises from negative sound speed squared.