Alcubierre metric and gravitational waves

[gildomar]

This may be a stupid question, but why can't the expansion/contraction of spacetime from a gravitational wave be used to create the areas of expansion/contraction required in the Alcubierre metric, instead of using regions of positive/negative energy density? I saw on the forums about the Alcubierre drive maybe producing gravitational waves as a consequence of it's operation, but not necessarily the other way around. Or has this already been addressed?

 

[bcrowell]

When you plug the Alcubierre metric into the Einstein field equations, you get a stress-energy tensor that violates various energy conditions (i.e., roughly speaking, negative mass-energy density is required).

If you want to propose some other metric with gravitational waves in it, then that will be some other metric, not the Alcubierre metric.

 

[dllahr]

Thanks for posting - my question was, if gravity waves propagate at the speed of light, how does the expansion-contraction of the Alcubierre metric travel faster? It seems they are not consistent with each other.