In this talk I will make a comprehensive review on the study of the in-time understanding about the late-time cosmic acceleration from the perspective of phenomenological studies. I will review the latest observational status of the late-time cosmic acceleration, and point out a new crisis about the observational tension of the Hubble constant. After that, I will depict how to proceed with various model buildings of dynamical dark energy. In the second part of the talk, I will introduce modified gravity, in particular, a type of torsional based modified gravity, which can also realize the late-time cosmic acceleration. This so-called f(T) gravity and beyond theories can be depicted in a language of effective field theory and thus we can examine certain operators that are most connected with various cosmological observations. Before ending, I will make an outlook on the new observational window of gravitational wave standard sirens.
Dr. Yi-Fu Cai is a professor of physics & astronomy at the University of Science and Technology of China. He received the Ph.D. from the Chinese Academy of Sciences in 2005. After that, he did postdoctoral research at Arizona State University from 2010 to 2012, and then, at McGill University from 2012 to 2015, respectively. He obtained the faculty position under the support of Chinese National Youth Talents Program in 2015. His research focuses on fundamental questions for cosmology and gravitation, namely, the big bang singularity, the origin and destiny of the universe, how the black holes and galaxies formed, as well as dark energy and modified gravity beyond Einstein. So far he has published more than 100 articles with the total citation of over 6000 times.