Revisiting wormhole energy conditions in Riemann-Cartan spacetimes and under Weyl transformations

We show that the violation of the null energy condition by matter, required by traversable wormholes, can be removed in spacetimes with torsion. In addition, we show that this violation can also be removed in the conformal frame obtained by a Weyl transformation. This comes about because both conformally transformed wormholes and wormholes in spacetimes with torsion become sustained thanks to a combination of “normal” matter, that satisfies the null energy condition, and an induced “geometric” energy-momentum tensor that is able to greatly violate the null energy condition.