Title：Exploring the dynamical nature of the late-time cosmic acceleration in light of DESI 2024

Speaker：蔡一夫，中国科学技术大学教授

Time：3:00 pm July 04th (Thursday)

Tencent Meeting：42915400486 password: 6360

Location: Lecture Hall, 3rd floor

Abstract：

Astonishingly, human beings discovered that distant Type Ia supernovae (SN Ia) were accelerating away at an increasing pace, following which further evidence from the cosmic microwave background (CMB), baryon acoustic oscillations (BAO), and large-scale structure (LSS) survey confirmed the accelerating expansion as well. This led to the great discovery of late-time cosmic acceleration and brought us the concept of dark energy, responsible for such a phenomenon, but the underlying nature remains mysterious. Using the latest Dark Energy Spectroscopic Instrument (DESI) data combined with other observations, we reconstructed the cosmological background evolution. Our results reveal that the reconstructed dark-energy equation-of-state (EoS) parameter w(z) exhibits the so-called quintom-B behavior, crossing −1 from phantom to quintessence regime as the universe expands. We investigate under what situation this type of evolution could be achieved from the perspectives of field theories and modified gravity. In particular, we reconstruct the corresponding actions for f(R), f(T), and f(Q) gravity, respectively. We conclude that, certain modified gravity can exhibit the quintom dynamics and fit the recent DESI data efficiently, and for all cases the quadratic deviation from the ΛCDM scenario is mildly favored.

CV：蔡一夫，中国科学技术大学教授，教育部国家重大人才工程入选者，主持国家重点研发计划引力波专项，担任中国天文学会理事、安徽省天文学会秘书长等职务，获得过国家创新人才青年项目、国家自然科学基金委优秀青年基金、中国天文学会黄授书奖等荣誉。研究领域是粒子宇宙学，兴趣集中在宇宙起源、大尺度结构的早期形成、暗物质暗能量等方面。在国际重要学术期刊上已发表学术论文160余篇，总被引用1万余次，连续多年入选爱思唯尔中国高被引学者、全球2%顶尖科学家等榜单。

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