http://www.newsweek.com/particle-physics-mind-bending-negative-mass-device-lasers-778495
Also see http://www.rochester.edu/newscenter/vamivakas-microcavity-negative-mass-generate-lasers-290202/ Also see https://en.wikipedia.org/wiki/Negative_mass Also see https://www.scientificamerican.com/article/are-wormholes-a-dead-end-for-faster-than-light-travel/ That's right: mass, but negative. A ring of negative-mass material could be used to construct a fully functional and useful wormhole. Since the exotic nature of negative mass warps spacetime in a unique way, it "inflates" the entrance to the wormhole outside the boundary of the event horizon, and stabilizes the throat of the wormhole against instabilities. It’s not an intuitive result but the math checks out.
