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Right sign of spin rotation operator

Quantum Physics 2018-01-19 v1 High Energy Physics - Experiment

Abstract

For the fermion transformation in the space all books of quantum mechanics propose to use the unitary operator U^n(φ)=exp(iφ2(σ^n))\widehat{U}_{\vec n}(\varphi)=\exp{(-i\frac\varphi2(\widehat\sigma\cdot\vec n))}, where φ\varphi is angle of rotation around the axis n\vec{n}. But this operator turns the spin in inverse direction presenting the rotation to the left. The error of defining of U^n(φ)\widehat{U}_{\vec n}(\varphi) action is caused because the spin supposed as simple vector which is independent from σ^\widehat\sigma-operator a priori. In this work it is shown that each fermion marked by number ii has own Pauli-vector σ^i\widehat\sigma_i and both of them change together. If we suppose the global σ^\widehat\sigma-operator and using the Bloch Sphere approach define for all fermions the common quantization axis zz the spin transformation will be the same: the right hand rotation around the axis n\vec{n} is performed by the operator U^n+(φ)=exp(+iφ2(σ^n))\widehat{U}^+_{\vec n}(\varphi)=\exp{(+i\frac\varphi2(\widehat\sigma\cdot\vec n))}.

Cite

@article{arxiv.1801.06129,
  title  = {Right sign of spin rotation operator},
  author = {R. A. Shindin and D. K. Guriev and A. N. Livanov and I. P. Yudin},
  journal= {arXiv preprint arXiv:1801.06129},
  year   = {2018}
}

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New version in English

R2 v1 2026-06-22T23:49:03.138Z