There are two standard forms of the equivalence principle. The Weak form states the equivalence of inertial and passive gravitational mass, which implies that all massive particles will fall along the same space-time trajectories in the presence of only gravitational effects. The Weak Principle is what is tested by the experiments of, e.g. Eötvos. Note that it has no consequences for the behavior of light. The Strong principle states the empirical equivalence of experiments done "at rest" in a constant gravitational field and in a constantly linearly accelerating lab with no gravity. That principle does have implication for light. But the Strong equivalence principle is restricted to comparing constant linear acceleration to a constant field. It does not even properly hold for labs on Earth, where the gravitational field is not constant, although the differences are of second order. (Consider stretching your hands apart and dropping two masses, measuring the distance between the hands and the distance between the place where they hit the floor. In a linearly accelerated system in flat space-time, those distances will be identical. In a lab on the Earth, they will not, since the gravitational field is not constant (they will hit slightly closer together, as they are both falling toward the center of the Earth, as it were. Similarly, a water droplet in a space station orbiting the Earth will be slightly elongated by tidal effects, and one in inertial motion in flat space-time will not. So not all "free-fall" is the same.)
The Strong Principle does not have any application at all for rotating systems. If you check your own reference (Misner, Thorne and Wheeler) you will verify this. Check Wald (for example) as well.
In the first part of this paper, two coordinate systems are laid down on flat space-time. Obviously, these coordinate systems do not change the space-time geometry at all: it is flat in both. The line element, of course, takes a different algebraic form relative to the different coordinates, as it must. This is just the same as using different coordinate systems on Euclidean space, and has no connection to the Equivalence Principle.
To clarify the situation, one cannot just talk about "accelerating" systems: the Strong Principle compares linearly accelerating systems in flat space-time to systems with a constant field. But rotation is not a linear acceleration. There is no gravitational field that will will mimic, as it were, the apparent effects of rotation. It you think any gravitational field can produce a "centrifugal" force, try to specify how. No stress-energy tensor will produce the same apparent physics is a non-rotating lab as there is in a rotating lab.
I see what Kündig states, but the claim is not accurate.
Regards,
Tim
