A research team has developed a…

A research team has developed a method to reduce uncertainties in measurements of cosmic birefringence, a subtle rotation in the polarization of the cosmic microwave background that may hold clues to new physics beyond the standard model. The work, published January 27 in Physical Review Letters, provides the first quantitative treatment of uncertainty in the birefringence angle, a key observable that could point to unknown physics breaking the universe's left right symmetry and help clarify the nature of dark matter and dark energy.

Cosmic birefringence refers to a small rotation in the polarization direction of the cosmic microwave background, the relic radiation from the Big Bang that preserves information about the early universe. Recent observations have hinted that the polarization of this ancient light is rotated, and this rotation is thought to be associated with hypothetical elementary particles known as axions that couple to light. To probe this effect, researchers analyze a signal called the CMB EB correlation, which encodes information about the rotation angle of the polarization plane.