Title: On the recent progress of axion cosmology

Abstract: Axions, hypothetical (pseudo) scalar particles supported by QCD and string theory, are promising candidates for the dark sector of our universe, such as inflation, dark matter and dark energy. It is known that axions topologically couple to the gauge fields and its dynamics could lead to a variety of parity-violating cosmological phenomena. In this talk, I will introduce a recent development of cosmological axion search, mainly focusing on the topics of chiral primordial gravitational waves from inflation and photon’s birefringence effects caused by axion as dark matter or dark energy, and discuss their observability in near future.