Information from the Beginning

Abstract

Requiring black hole evaporation to be quantum-mechanically coherent imposes a universal, finite ``holographic bound'', conjectured to be due to fundamental discreteness of quantized gravity, on the amount of information carried by any physical system. This bound is applied to the information budget in the standard slow-roll model of cosmic inflation. A simple estimate suggests that when quantum gravity is included, fluctuations during inflation have a discrete spectrum with a limited information content, only about 10^5 bits per mode, fixed by the inverse scalar perturbation amplitude. This scarcity of information may allow direct observation of quantum-gravity eigenmodes in the anisotropy of cosmic background radiation.