Abstract
We investigate locally rotational symmetric (LRS) Bianchi type I space time coupled with scalar field. String cosmological models generated by a cloud of strings with particles attached to them are studied in the Brans-Dicke theory. We assume that the expansion scalar is proportional to the shear scalar and also power law ansatz for scalar field. The physical behavior of the resulting model is discussed through different parameters.
Highlights
It is believed that the early universe evolved through some phase transitions, thereby yielding a vacuum energy density which at present is at least 118 orders of magnitudes smaller than in the Planck time [1]
Among the various modifications of general relativity (GR), the Brans-Dicke (BD) theory of gravity [4] is a well-known example of a scalar tensor theory in which the gravitational interaction involves a scalar field and the metric tensor
Since the field equations contain A and B and their derivatives, so without any loss of generality, we shall assume that the BD scalar field φ is some power of the average scale factor; that is, the power law relation between scale factor a and scalar field φ has already been used by Johri and Desikan [5] in the context of Robertson Walker Brans-Dicke models
Summary
It is believed that the early universe evolved through some phase transitions, thereby yielding a vacuum energy density which at present is at least 118 orders of magnitudes smaller than in the Planck time [1] Such a discrepancy between theoretical expectations and empirical observations constitutes a fundamental problem in the interface uniting astrophysics, particle physics, and cosmology. To provide predictions for the CMB anisotropies, one may consider the homogeneous but anisotropic cosmologies known as Bianchi type space times, which include the isotropic and homogeneous FRW models. Reddy et al [8] discussed the homogeneous axially symmetric Bianchi type-I radiating cosmological model with negative constant deceleration parameter in BD scalar-tensor theory gravitation. We consider a spatially homogeneous and anisotropic LRS Bianchi type-I cosmological model in BransDicke scalar-tensor theory of gravitation in the presence of cosmic string source. The resulting cosmological model can be considered as an analogue of inflationary model in BransDicke string cosmology
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