Spacetime Conformal Fluctuations and Quantum Dephasing

TL;DR

This paper investigates how spacetime conformal fluctuations, modeled via a stochastic approach, induce quantum dephasing and explores their physical origins within scalar-tensor theories like Brans-Dicke, with implications for quantum gravity and vacuum energy.

Contribution

It introduces a framework for analyzing conformal metric fluctuations' role in quantum dephasing and examines their natural emergence in scalar-tensor gravity theories.

Findings

Conformal fluctuations cause quantum dephasing through an effective nonlinear Newtonian potential.

Standard General Relativity does not support spontaneous conformal modulations.

Scalar-tensor theories like Brans-Dicke naturally produce conformal fluctuations affecting quantum systems.

Abstract

Any quantum system interacting with a complex environment undergoes decoherence. Empty space is filled with vacuum energy due to matter fields in their ground state and represents an underlying environment that any quantum particle has to cope with. In particular quantum gravity vacuum fluctuations should represent a universal source of decoherence. To study this problem we employ a stochastic approach that models spacetime fluctuations close to the Planck scale by means of a classical, randomly fluctuating metric (random gravity framework). We enrich the classical scheme for metric perturbations over a curved background by also including matter fields and metric conformal fluctuations. We show in general that a conformally modulated metric induces dephasing as a result of an effective nonlinear newtonian potential obtained in the appropriate nonrelativistic limit of a minimally coupled Klein-Gordon field. The special case of vacuum fluctuations is considered and a quantitative estimate of the expected effect deduced. Secondly we address the question of how conformal fluctuations could physically arise. By applying the random gravity framework we first show that standard GR seems to forbid spontaneous conformal metric modulations. Finally we argue that a different result follows within scalar-tensor theories of gravity such as e.g. Brans-Dicke theory. In this case a conformal modulation of the metric arises naturally as a result of the fluctuations in the Brans-Dicke field and quantum dephasing of a test particle is expected to occur. For large negative values of the coupling parameter the conformal fluctuations may also contribute to alleviate the well known problem of the large zero point energy due to quantum matter fields.