When galaxies merge, the super-massive black holes at their center can merge as well. General relativity predicts that the newly merged black hole can, in forming, be kicked with a large velocity out of the galactic center!
Gravity can induce global instabilities in disks around stars, which then collapse to form planets at different radii.
Today’s authors propose that, in addition to the first stars, the first stellar black holes might have contributed significantly to the period of cosmic reionization.
Magnetic fields can get hugely amplified when gas clouds gravitationally collapse. The authors of this paper explore gravitational collapse using MHD simulations and argue for a new resolution requirement in order to properly resolve magnetic dynamo action on small scales.
Using the anthropic principle to explain the cosmological constant requires some way to determine probabilities over the multiverse. But strangely enough, this predicts that the probability of finding yourself in a Universe with a positive cosmological constant (like ours) is exactly 0. The authors of this work argue that this is not a fatal blow to anthropic reasoning or the multiverse hypothesis.