Testing Parity-Violating Mechanisms with Cosmic Microwave Background
  Experiments
  Chiral gravity and cosmological birefringence both provide physical
mechanisms to produce parity-violating TB and EB correlations in the cosmic
microwave background (CMB) temperature/polarization. Here, we study how well
these two mechanisms can be distinguished if non-zero TB/EB correlations are
found. To do so, we evaluate the correlation matrix, including new TB-EB
covariances. We find that the effects of these two mechanisms on the CMB are
highly orthogonal, and can thus be distinguished fairly well in case of a
high--signal-to-noise detection of TB/EB correlations. An Appendix evaluates
the relative sensitivities of the BB, TB, and EB signals for detecting a chiral
gravitational-wave background.
