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

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.

Hidden symmetries from distortions of the conformal structure

“…One motivation behind the introduction of disformal transformations, was to connect different scalar-tensor theories [56]. For further uses and applications of disformal transformations see [57][58][59][60][61][62]. We may generalize (2.42), by defining a transformation of the form ĝµν = A(x)g µν + B(x)K µν , with K any second rank tensor, which would be compatible with (2.37).…”