...The reason physicists have been skeptical about wormholes comes down to a problem with energy. To hold the throat of a wormhole open, you would need something called exotic matter. In physics, ordinary matter (stars, gas, you, your coffee) always has a positive energy density which corresponds to positive mass. Exotic matter would have negative energy density, essentially “negative mass.” We have never observed anything like that in nature. Most wormhole solutions that physicists have found over the decades require this exotic matter to exist, which is why wormholes have stayed firmly in the category of “mathematically possible but physically unlikely.” Today’s paper offers a way around this problem.

Instead of trying to prop open a wormhole with exotic matter, the authors add two extra physical fields to Einstein’s equations alongside gravity. The first is an electromagnetic field, the same electric and magnetic fields you encounter in introductory physics. This wormhole carries both electric and magnetic charge. The second is something called a dilaton...

Why should we care about the dilaton? Because it is not something the authors invented for convenience. It shows up naturally in several theories that physicists take seriously as candidates for deeper laws of nature. Superstring theory, which attempts to unify all fundamental forces, predicts a dilaton. So does Kaluza-Klein theory, which tries to explain electromagnetism as a consequence of a hidden extra dimension of space. And Brans-Dicke theory includes one too. If any of these theories are correct, the dilaton exists, and the kind of wormhole described in this paper becomes a natural prediction of Einstein’s equations...