Gravity in twisted space
Numerical simulations with periodic boundary conditions are widely used in cosmology. These have a multiply connected topology known as a three-torus. Such nontrivial topologies for the actual universe may have arisen in the Big Bang. A two-dimensional numerical model with a twisted topology, sometimes a Klein bottle, is shown as well as the fact that local properties of the model are not dependent on topology.
Farrar, Kelly A.↗