Note the paper discusses some proposals of positive-energy warp drives. The well-known Alcubierre drive[1] requires negative energy density. So while it dodges

Note the paper discusses some proposals of positive-energy warp drives. The well-known Alcubierre drive[1] requires negative energy density. So while it dodges the critique of this paper, negative energy is highly likely to be unphysical. And no, what Michio Kaku fantasized on that Discovery show won't work as the Casimir effect isn't due to vacuum energy[2][3] and thus you can't get negative energy that way. [1]: https://en.wikipedia.org/wiki/Alcubierre_drive https://en.wikipedia.org/wiki/Alcubierre_drive [2]: https://arxiv.org/abs/1605.04143 https://arxiv.org/abs/1605.04143 [3]: https://arxiv.org/abs/hep-th/0503158 https://arxiv.org/abs/hep-th/0503158