Title: 基于DESI 2025数据驱动下宇宙加速膨胀的理论探究 /

  Theoretical perspectives on the late-time cosmic acceleration after DESI 2025

Speaker: 蔡一夫

Institute: 中国科学技术大学

Host: 刘彤

Time: 2025.11.19 周三 14:30

Location: 物理楼 552

Abstract:

Astonishingly, human beings discovered that distant Type Ia supernovae (SN Ia) were accelerating away at an increasing pace. 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. Theoretically, modified gravity can be a framework to provide an alternative explanation for the existence of dark energy. In this talk, we will go further into the effective field theory of dark energy in light of the latest cosmological observations. In particular, using the latest Dark Energy Spectroscopic Instrument (DESI) data combined with other observations, we reconstructed the cosmological background evolution and find 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. In particular, we reconstruct the corresponding actions for f(R), f(T), and f(Q) gravity, respectively. Our analyses indicate that, certain modified gravity such as metric-affine gravity could 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.

Bio:

Yi-Fu Cai is a professor of physics and astronomy at the University of Science and Technology of China. He is also an honorary Yangtse River Scholar of China. He received the PhD degree in theoretical physics at the Institute of High Energy Physics, Chinese Academy of Sciences in 2010. He worked as a postdoc at Arizona State University and McGill University until 2015. He was selected into the China's National Youth Talents Program in 2015 and became a faculty at USTC. His particle cosmology group is responsible for the scientific goals of the AliCPT project associated with cosmological models. His research focuses on fundamental questions for physical cosmology including the big bang singularity, the origin of the universe, dark energy and cosmic acceleration, cosmological perturbation theory as well as the CMB sciences.

蔡一夫，中国科学技术大学教授，国家重大人才工程特聘教授，国家重点研发计划引力波专项首席，担任中国天文学会理事、安徽省天文学会秘书长等职务，获得过基金委重点、优青、国家创新人才青年项目、国合面上、中国科协青年托举工程等资助，以及中国天文学会黄授书奖等荣誉。2001-2005年，中国科学技术大学攻读本科；2005-2010年，中国科学院高能物理研究所硕博连读；2010-2012年，美国亚利桑那州立大学第一期博士后；2012-2015年，加拿大麦吉尔大学第二期博士后。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论文200余篇，总被引用一万三千余次，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。

References: 

2404.19437 (Sci.Bull), 2501.18336 (JCAP), 2504.06784 (ApJ)