  We compute the one-loop quantum corrections to the gravitational potentials
of a spinning point particle in a de Sitter background, due to the vacuum
polarisation induced by conformal fields in an effective field theory approach.
We consider arbitrary conformal field theories, assuming only that the theory
contains a large number $N$ of fields in order to separate their contribution
from the one induced by virtual gravitons. The corrections are described in a
gauge-invariant way, classifying the induced metric perturbations around the de
Sitter background according to their behaviour under transformations on
equal-time hypersurfaces. There are six gauge-invariant modes: two scalar
Bardeen potentials, one transverse vector and one transverse traceless tensor,
of which one scalar and the vector couple to the spinning particle. The quantum
corrections consist of three different parts: a generalisation of the
flat-space correction, which is only significant at distances of the order of
the Planck length; a constant correction depending on the undetermined
parameters of the renormalised effective action; and a term which grows
logarithmically with the distance from the particle. This last term is the most
interesting, and when resummed gives a modified power law, enhancing the
gravitational force at large distances. As a check on the accuracy of our
calculation, we recover the linearised Kerr-de Sitter metric in the classical
limit and the flat-space quantum correction in the limit of vanishing Hubble
constant.

High Energy Physics - Theory;General Relativity and Quantum Cosmology