The existence of axions is suggested by theoretical ideas that would bring our understanding of (approximate) time reversal symmetry to a new level of perfection. Their predicted properties are remarkably definite, but quite unusual. If axions exist, they plausibly supply the cold dark matter that cosmologists require. Experiments to confirm or refute these ideas are challenging, but promising approaches have been proposed, and many physicists are taking up the search.
click here for more details- Seminar by Frank Wilczek