# On the Non-uniqueness Problem of the Covariant Dirac Theory and the Spin-Rotation Coupling

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## Abstract

Gorbatenko and Neznamov [arXiv:1301.7599, 2013] recently claimed the absence of the title problem. In this paper, the reason for that problem is reexplained by using the notions of a unitary transformation and of the mean value of an operator, invoked by them. Their arguments actually aim at proving the uniqueness of a particular prescription for solving this problem. But that prescription is again shown non-unique. Two Hamiltonians in the same reference frame in a Minkowski spacetime, only one of them including the spin-rotation coupling term, are proved to be physically non-equivalent. This confirms that the reality of that coupling should be checked experimentally.

## Keywords

Dirac Hamiltonian Curved spacetime Unitary transformation Rotating frame## Notes

### Acknowledgement

It was noted by M. V. Gorbatenko & V. P. Neznamov (private communication) and by a referee that, in the first version of this paper, it was not accounted for the fact that the energy can usually be subjected to a constant shift. The referee suggested a definition of physically equivalent energy operators which is equivalent to the one given below.

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