Disformal transformations and the motion of a particle in semi-classical gravity

TL;DR

This paper explores how disformal transformations can incorporate quantum effects into gravity by modifying the geometry, providing solutions to issues faced in conformal approaches and extending the geometric description of quantum particle motion.

Contribution

It introduces a framework using disformal transformations to embed quantum effects in gravity, addressing limitations of conformal methods in describing quantum particle trajectories.

Findings

Disformal transformations can encode quantum effects within the geometry.

They resolve issues like incorrect continuity equations and mass indefiniteness.

The approach improves the description of massless particles near singularities.

Abstract

The approach to incorporate quantum effects in gravity by replacing free particle geodesics with Bohmian non-geodesic trajectories has an equivalent description in terms of a conformally related geometry, where the motion is force free, with the quantum effects inside the conformal factor, i.e., in the geometry itself. For more general disformal transformations relating gravitational and physical geometries, we show how to establish this equivalence by taking the quantum effects inside the disformal degrees of freedom. We also show how one can solve the usual problems associated with the conformal version, namely the wrong continuity equation, indefiniteness of the quantum mass, and wrong description of massless particles in the singularity resolution argument, by using appropriate disformal transformations.