Decoherence of cosmological perturbations from boundary terms and the non-classicality of gravity

bstract We note that the decoherence of inflationary curvature perturbation ζ is dominated by a boundary term of the gravity action. Although this boundary term cannot affect cosmological correlators 〈 ζ n 〉, it induces much faster decoherence for ζ than that of previous calculations. The gravitational origin of inflationary decoherence sheds light on the quantum (or non-classical) nature of gravity. By comparing with a Schrödinger-Newton toy model of classical gravity, we show that gravity theories of classical or quantum origins can be distinguished by comparing their different impacts on decoherence rate of ζ . Our calculation also indicates that density fluctuation δρ better preserves quantum information than ζ for the purpose of constructing cosmological Bell-like experiments.