Cosmic Birefringence: Is the Universe Left-Handed or Right-Handed?
Speaker: Tomohiro Fujita (Ochanomizu University)
Abstract:
Light from the cosmic microwave background, the afterglow of the Big Bang, has traveled through the Universe for 13.8 billion years before reaching us. Recent observations suggest that, during this long journey, its polarization direction may have rotated slightly, by about 0.3 degrees. If this signal is real, it would mean that the Universe is not perfectly symmetric between left and right on the largest observable scales. Such a tiny rotation may therefore carry information about new physics filling cosmic space, possibly related to dark energy. In this colloquium, I will introduce the observational idea of cosmic birefringence and discuss why this subtle twist of light could be an important clue to the fundamental nature of the Universe.