  Maldacena and Susskind conjectured that two entangled particles, which can be
thought of as forming an Einstein-Podolsky-Rosen (EPR) pair, are connected by a
nontraversable wormhole or Einstein-Rosen (ER) bridge. They named their
conjecture ER = EPR. We present a concrete quantitative model for ER = EPR, in
which two spin-1/2 particles in a singlet state are connected by a
nontraversable wormhole in asymptotically flat general relativity. In our
model, the fermions are described by the charged Dirac equation minimally
coupled to gravity. This system has static wormhole solutions. We use these
solutions as initial data and numerically evolve them forward in time. Our
simulations show that black holes form, which are connected by the wormhole and
which render the wormhole nontraversable. We also find that the wormhole throat
shrinks, which places the particles in close proximity to one another and
suggests an explanation for how the wormhole facilitates the nonlocal
communication required by entanglement.
