Robin Hanson, <firstname.lastname@example.org>, writes:
> Hal F. wrote:
> >Everyone seems to be ignoring Anders' post of a proof that wormholes can't
> >exist. The current state of play is that there ain't no such animals.
> The abstract of that paper said that it assumed positive energy density.
> Which just confirms that you need some negative energy to get wormholes.
Yes, this is true. However the very last paragraph of the paper claims that the result is more general:
Finally, although the sketch of the topological censorship theorem uses the null energy condition, one can show that it actually can be rigorously proven for a weaker energy condition, the averaged null energy condition. Physically this energy condition states that the energy can be negative in small regions so long as it is positive when averaged over the whole spacetime. This implies that the topological censorship theorem can be applied not only to spacetimes with classical matter but may also apply to spacetimes containing certain types of quantum matter.
The paper is at http://xxx.lanl.gov/ps/gr-qc/9903061.