Physical Review D - Particles, Fields, Gravitation, and Cosmology
A cosmological gauge field with isotropic stress-energy introduces parity violation into the behavior of gravitational waves. We show that a primordial spectrum of inflationary gravitational waves develops a preferred handedness, left or right circularly polarized, depending on the abundance and coupling of the gauge field during the radiation era. A modest abundance of the gauge field would induce parity-violating correlations of the cosmic microwave background temperature and polarization patterns that could be detected by current and future experiments.
Bielefeld, Jannis and Caldwell, Robert R., "Chiral Imprint of a Cosmic Gauge Field on Primordial Gravitational Waves" (2015). Open Dartmouth: Faculty Open Access Articles. 1958.