Density perturbations in the Brans-Dicke theory
The authors investigate the behavior of linearized density perturbations in the scalar-tensor theory of gravity proposed by Brans and Dicke. Four equations of state for the cosmic substratum are distinguished: vacuum, inflation, dust and radiation. The background solutions are assumed as spatially flat with a power-law for the expansion of the scale factor and the scalar field. In all cases the density perturbations an be described by Bessel functions. Their behaviour (growing and decaying modes) is discussed in detail.
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