solitons are a wave effect that is self-reinforcing. solitons can maintain their shape while moving at a constant velocity and have been observed in water and other fluids. lentz demonstrated that while soliton warp bubbles would require an incredible amount of dense matter, it wouldn't require the energy of the matter to be negative https://www.universetoday.com/150510/alcubierre-gives-us-an-update-on-his-ideas-about-warp-drives/#more-150510