De Sitter scattering amplitudes in the Born approximation

We present a covariant framework to compute scattering amplitudes and potentials in de Sitter background. In this setting, we the potential of graviton-mediated process involving two very massive scalars at tree level. Although obtained reproduces Newtonian short distances, on Hubble-size length scales it is affected by constant curvature: effectively, yields repulsive force sub-Hubble distances. This can be attributed expansion universe. Beyond horizon, vanishes identically. Hence, amplitude unveils geometric properties spacetime novel nontrivial way.