In one minute

Carlos Barceló and Matt Visser show how a simple, apparently harmless classical scalar field theory can violate the energy conditions. A scalar field coupled non-minimally to curvature with positive coupling easily violates every standard energy condition, including the averaged null energy condition. Solving gravity with such a massless field for static spherical configurations, they find a whole branch of traversable wormholes for every positive coupling. This generalises their earlier conformal coupling case of one sixth. For these wormholes to exist, the scalar field must reach trans-Planckian values somewhere, and the authors discuss how current theoretical physics can accommodate that.

Scalar fields, energy conditions and traversable wormholes