### Abstract

We propose Lagrangian formulation for the particle with value of spin fixed within the classical theory. The Lagrangian is invariant under non-Abelian group of local symmetries. On this reason, all the initial spin variables turn out to be unobservable quantities. As the gauge-invariant variables for description of spin we can take either the Frenkel tensor or the Bargmann-Michel-Telegdi (BMT) vector. Fixation of spin within the classical theory implies O(h)-corrections to the corresponding equations of motion.

Original language | English |
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Article number | 1250234 |

Journal | Modern Physics Letters A |

Volume | 28 |

Issue number | 1 |

DOIs | |

Publication status | Published - 10 Jan 2013 |

### Keywords

- Bargmann-Michel-Telegdi equation
- Frenkel equation
- Semiclassical description of relativistic spin
- Theories with constraints

### ASJC Scopus subject areas

- Nuclear and High Energy Physics
- Astronomy and Astrophysics

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## Cite this

Deriglazov, A. A. (2013). Variational problem for the frenkel and the Bargmann-Michel-Telegdi (BMT) equations.

*Modern Physics Letters A*,*28*(1), [1250234]. https://doi.org/10.1142/S0217732312502343