The name tachyonic antitelephone is a bit unfortunate because it need not involve tachyons. All it takes is the ability to send a message outside of your light cone. Along the path actually taken need not be the case, we are reasoning about the endpoints of the communication independent of the means.
In particular it does not matter whether you use a warp drive or not. The violation occurs relative to reference frames outside of the warp bubble where special relativity fully applies. Here, explicitly looks like a worked out example: http://exvacuo.free.fr/div/Sciences/Dossiers/Time/A%20E%20Ev...
You can create instances of FTL travel or communication that don't violate causality. But the ability to perform such FTL tricks implies the possibility of constructing a closed timelike curve so long as you're talking about a localized phenomenon like a warp drive or tachyon where special relativity holds outside of a negligible area.
If you're messing with the global geometry of spacetime then you can make very weird things happen and I would not be surprised if there were such a geometry that allows FTL communication in a limited way that doesnt allow CTCs. But that would not like our universe or a warp drive, a specifically localized situation.
In particular it does not matter whether you use a warp drive or not. The violation occurs relative to reference frames outside of the warp bubble where special relativity fully applies. Here, explicitly looks like a worked out example: http://exvacuo.free.fr/div/Sciences/Dossiers/Time/A%20E%20Ev...
You can create instances of FTL travel or communication that don't violate causality. But the ability to perform such FTL tricks implies the possibility of constructing a closed timelike curve so long as you're talking about a localized phenomenon like a warp drive or tachyon where special relativity holds outside of a negligible area.
If you're messing with the global geometry of spacetime then you can make very weird things happen and I would not be surprised if there were such a geometry that allows FTL communication in a limited way that doesnt allow CTCs. But that would not like our universe or a warp drive, a specifically localized situation.