[pierre_d528]

Or we could shift to an other side of the universe by "inverting" the mass of the ship where the speed of light is much higher[1].

Cosmology is so cool... too bad we do not have time for that: we cannot even cure the common cold!

[1]: https://januscosmologicalmodel.com/pdf/2014-ModPhysLettA.pdf Cosmological bimetric model with interacting positive andnegative masses and two different speeds of light,in agreement with the observed acceleration of the Universe

[atonalfreerider]

> Special Relativity can be summed up in the sentence: “We live in a spacetime which is an M4 manifold with a hyperbolic Lorentz metric of signature (+−−−)”. General Relativity can be stated accordingly: “The Universe is an M4 manifold with a Riemannian metric of signature (+−−−)” which is a solution of the Einstein equation:Rμν−12Rgμν+Λgμν=χTμν.

It sounds like you get anti-gravity for free along the way to getting superluminal travel.

[pierre_d528]

No because no "run away" effect. "inverted" mass means that the mass goes on the other side... gravity works the same there.