Noncritical Liouville string escapes constraints on generic models of quantum gravity

Abstract

It has recently been pointed out that generic models of quantum gravity must contend with severe phenomenological constraints imposed by gravitational Čerenkov radiation, neutrino oscillations and the cosmic microwave background radiation. We show how the noncritical Liouville-string model of quantum gravity we have proposed escapes these constraints. It gives energetic particles subluminal velocities, obviating the danger of gravitational Čerenkov radiation. The effect on neutrino propagation is naturally flavor independent, obviating any impact on oscillation phenomenology. Deviations from the expected blackbody spectrum and the effects of time delays and stochastic fluctuations in the propagation of cosmic microwave background photons are negligible, as are their effects on observable spectral lines from high-redshift astrophysical objects.