Consistency
It is still not known whether Einstein æther theories exist as quantum theories. One immediate concern might be that the time vector, which breaks Lorentz invariance, will lead to Faddeev–Popov ghosts which fail to decouple and ruin the theory. This problem is avoided because the vector is of unit length in a timelike direction, and so its oscillations are spacelike. Therefore it does not contribute extra time derivatives to the denominator of the propagator, which could have led to poles with a wrong-sign residue and so could have ruined the unitarity of the S-matrix.
Read more about this topic: Einstein Aether Theory
Famous quotes containing the word consistency:
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—Walter Benjamin (1892–1940)
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—Henry David Thoreau (1817–1862)
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