In general relativity, the fundamental notions are the curvature (Ricci tensor) and the stress energy tensor. Energy density and curvature are connected .
The Casimir vacuum between parallel plates could fulfill the negative energy density requirements (positive energy density for Casimir spherical shells as far as I know , but I don't have strong references in this direction).
In vacuum, in the absence of any other forces or fields, does matter tend to follow the gradient of the vacuum energy density ( for example from high vacuum energy density to low vacuum energy density )?
In vacuum, in the absence of any other forces, a ship with a large number of Casimir plates at one end (I won't bother to put spherical shells at the other end), will it tend to move without the need of any fuel (as slow as it may)?
A picture's worth a thousand words. View here .
In this design the Casimir plates are parallel to the direction of travel. A similar design could be considered, where the Casimir plates are orthogonal to the direction of travel.The ship moves for the same reason the plates are pushed together in the original Casimir experiment, following the gradient of the vacuum energy density.
If not, please explain.