  The ultrarelativistic boosting procedure had been applied in the literature
to map the metric of Schwarzschild-de Sitter spacetime into a metric describing
de Sitter spacetime plus a shock-wave singularity located on a null
hypersurface. This paper evaluates the Riemann curvature tensor of the boosted
Schwarzschild-de Sitter metric by means of numerical calculations, which make
it possible to reach the ultrarelativistic regime gradually by letting the
boost velocity approach the speed of light. Thus, for the first time in the
literature, the singular limit of curvature through Dirac's delta distribution
and its derivatives is numerically evaluated for this class of spacetimes.
Eventually, the analysis of the Kretschmann invariant and the geodesic equation
show that the spacetime possesses a scalar curvature singularity within a
3-sphere and it is possible to define what we here call boosted horizon, a sort
of elastic wall where all particles are surprisingly pushed away, as numerical
analysis demonstrates. This seems to suggest that boosted geometries are ruled
by a sort of antigravity effect since all geodesics seem to refuse to enter the
boosted horizon, even though their initial conditions are aimed at driving the
particles towards the boosted horizon.
