On the initial singularity in the scalar-tensor anisotropic cosmology

Abstract

In connection with the problem of the initial singularity in the scalar-tensor anisotropic cosmology of Jordan-Brans-Dicke, the dynamics of homogeneous models of Bianchi type I is examined on the basis of the general analytic solutions in vacuo and in the presence of gravitating matter with state equations P=nɛ (0 ⩽ n ⩽ 1). It is shown that the scalar homogeneous ϑ-field, as an effective source of the V4geometry, has to influence essentially the dynamics of the early anisotropic stage of the Universe's expansion, and significantly modifies the character of the initial singularity. At negative ω (ω < −6), the sourceless scalar ϑ-field may remove the singularity and provide regular ‘bouncing’ in the models with matter (P ⩽ ɛ/3) if it prevails over the tensor anisotropic mode of the vacuum gravitational field.