Chiral vacuum fluctuations in quantum gravity
  We examine tensor perturbations around a deSitter background within the
framework of Ashtekar's variables and cousins parameterized by the Immirzi
parameter $\gamma$. At the classical level we recover standard cosmological
perturbation theory, with illuminating insights. Quantization leads to real
novelties. In the low energy limit we find a second quantized theory of
gravitons which displays different vacuum fluctuations for right and left
gravitons. Nonetheless right and left gravitons have the same (positive)
energies, resolving a number of paradoxes suggested in the literature. The
right-left asymmetry of the vacuum fluctuations depends on $\gamma$ and the
ordering of the Hamiltonian constraint, and it would leave a distinctive
imprint in the polarization of the cosmic microwave background, thus opening
quantum gravity to observational test.
