On the geometric foundation of classical gauge gravitation theory Gennadi Sardanashvily Department of Theoretical Physics, Physics Faculty, Moscow State University, 117234 Moscow, Russia E-mail:
[email protected] Abstract. A number of recent works in E-print arXiv have addressed the foundation of gauge gravitation theory again. As is well known, differential geometry of fibre bundles provides the adequate mathematical formulation of classical field theory, including gauge theory on principal bundles. Gauge gravitation theory is formulated on the natural bundles over a world manifold whose structure group is reducible to the Lorentz group. It is the metric-affine gravitation theory where a metric (tetrad) gravitational field is a Higgs field. 1 Introduction The present exposition of gauge gravitation theory follows Refs. [42, 63, 64]. By a world manifold throughout is meant a four-dimensional oriented smooth manifold coordinated by (xλ). Let us first recall the notion of a gauge transformation [16, 42, 43]. In the physical literature, by a (general) gauge transformation is meant a bundle automorphisms Φ of a fibre bundle Y → X over a diffeomorphism f of its base X. If f = Id X, the Φ is said to be a vertical gauge transformation. If P → X is a principal bundle with a structure Lie group G, a gauge transformation Φ of P is an equivariant automorphism of P , i.e., Φ◦Rg = Rg ◦Φ, g ∈ G, where Rg denotes the canonical right action of G on P on the right. A diffeomorphism f of X need not give rise to an automorphism a fibre bundle Y → X, unless Y belongs to the category of natural bundles over X.