  We study the bootstrapped Newtonian potential generated by a localised source
in one and two spatial dimensions, and show that both cases naturally lead to
finite spatial extensions of the outer vacuum. We speculate that this implies
the necessary existence of a cosmological (particle) horizon associated with
compact sources. In view of the possible dimensional reduction occurring in
ultra-high energy processes - like scatterings at Planckian energies, the
gravitational collapse of compact objects or the end-point of black hole
evaporation - one can consider such lower-dimensional "bubbles" immersed in our
Universe as describing (typically Planckian size) baby universes relevant to
those dynamics.
