Future Island Universes in an Accelerating Background Universe

Recent data from cosmological supernova measurements show that our universe is in accelerating expansion. If such expansion lasts forever, one would have expected the universe to approach a state of cold death, where all points are pulled apart faster than light can travel. However, many local regions in the universe can still be protected by their own gravity and defy such a cosmic pull to form mini-universes, provided that their present local matter-density parameter $\Omega_{i,0}>2.36$. The Local Group is in one of them. These future self-bound regions, within which local physics remains the same as today, will eventually fall onto each other's horizon and become island universes. Such mini-universes typically weigh less than $2\times 10^{14}$ solar masses, with the light ones having tight and compact configurations.