What principles of physics restrict a disintegration ray? If a vehicle were to move horizontally through solid stone by separating it into pieces, moving the pieces behind it, and reassembling them precisely as they were, the net change in energy ought to be zero.  The actual cost of boring a hole appears to depend on the immense inefficiency of grinding up material through friction or, more exotically, converting it to vapor with a laser drill.
Suppose you have some wild notion such as using coherent phonons produced by a computer-adjusted array to constructively interfere into sudden shear waves in front of the vehicle every millimeter or so.  Is there any principle of physics you could use to say that this needs to cost no less than some specified amount of energy per gram of rock moved, or can't be done at all?
 A: A basic principle behind the minimum energy requirement is that of a potential barrier.
Consider a very simplified model: the object to disintegrate is a pair of oppositely charged particles which are at a small distance apart. There is an electrostatic attraction between them, so they have less energy being close than they would have if they were far away.
Specifically, the energy $E$ of the system of two stationary particles is in the form
$$
E = - \frac{k}{r}
$$
where $k$ is some constant, while $r$ is the separation between the particles.
Disintegrating the object in this context would entail moving these far apart (say, with very large $r$, so that $E \approx 0$).
Now you can see that, even if you later go back to the situation with small $r$ (and thus negative energy), if you want to pass through the condition of the two particles being far apart you must give them enough energy to reach it.
This is all for a perfectly efficient process: the thing is, molecules and atoms in materials are bound together so that the energy they have when they are close is less than that they have when they are far away.
For a real-world process one would surely have to account for all kinds of inefficiencies, but the number of bonds to break and re-form will give a hard lower limit on the energy needed.
