No abstract

No abstract

No abstract

No abstract

Dirac fermion fields are responsible for spontaneous symmetry breaking in gauge gravitation theory because the spin structure associated with a tetrad field is not preserved under general covariant transformations. Two solutions of this problem can be suggested. (i) There exists the universal spin structure S → X such that any spin structure S h → X associated with a tetrad field h is a subbundle of the bundle S → X. In this model, gravitational fields correspond to different tetrad (or metric) fields. (ii) A background tetrad field h and the associated spin structure S h are fixed, while gravitational fields are identified with additional tensor fields q λ µ describing deviations h λ a = q λ µ h µ a of h. One can think of h as being effective tetrad fields. We show that there exist gauge transformations which keep the background tetrad field h and act on the effective fields by the general covariant transformation law. We come to Logunov's Relativistic Theory of Gravity generalized to dynamic connections and fermion fields.