Implications of the Cosmic Birefringence Measurement for the Axion Dark
  Matter Search
  We show that a recent constraint on the cosmic birefringence effect due to
dark energy can be related to the constraints on the coupling of axion dark
matter to photon, by relying on a simple model of two-axion alignment mechanism
with periodic potentials. Owing to the alignment of the potentials, one linear
combination of two fields provides a nearly flat direction and acts as dark
energy, whereas the other combination provides a steep direction and acts as
dark matter. This scenario solves the known conceptual issues of one-field
model for dark energy and predicts the connection between seemingly disparate
constraints on the dark sectors of our universe.
