报告题目：Probing dark energy and modified gravity from large-scale structure of the Universe

报 告 人：Teppei Okumura (The University of Tokyo)

报告时间：3月26日（周四）13:30-15:00

报告地点：物理系三楼报告厅

报告摘要：The discovery of the cosmic acceleration has established the current standard cosmological scenario known as the LCDM model, which is consistent with all the recent observations including cosmic microwave background (CMB), type Ia supernovae, weak lensing, large-scale structure, etc. However, the origin of the observed acceleration, called dark energy, is still unknown at all thus is a serious problem not only for astronomy but also for fundamental physics. The simplest candidate for dark energy is Einstein's cosmological constant, where the dark energy equation of state is a constant, w=-1. There are also attempts to explain the acceleration without relying on dark energy by modifying Einstein's general relativity. Astronomical observations are currently only the way to distinguish these different candidates. To obtain a better understanding of dark energy, the large-scale structure (LSS) observation is considered to be one of the most powerful cosmological tools because one can obtain 3-dimensional matter distribution through galaxy redshift surveys, while CMB probes the 2-d projection along the line of sight.

In this talk, first I will review how to extract cosmological information from observed galaxy distribution in galaxy surveys. Then I will present current observational constraints on dark energy properties from galaxy surveys. There are many large ongoing and upcoming galaxy surveys to constrain properties of dark energy at percent level. I will show some theoretical issues when one tries to apply current theoretical model of galaxy clustering to obtain the one percent accuracy. Then I will present a theoretical formalism of galaxy clustering I have developed. Finally, I will talk about the remaining issues, that are how to make a better connection between observed galaxy clustering in precision galaxy surveys and properties of dark energy.