Global Monopoles in Brans-Dicke Theory of Gravity

The gravitational field of a global monopole in the context of Brans-Dicke theory of gravity is investigated. The space-time and the scalar field generated by the monopole are obtained by solving the field equations in the weak field approximation. A comparison is made with the corresponding results predicted by General Relativity. Electronic address: [email protected] 1 Monopoles resulting from the breaking of globalO(3) symmetry lie among those strange and exotic objects like cosmic strings and domain walls [1], generally referred to as topological defects of space-time, which may have existed due to phase transitions in the early universe. Likewise cosmic strings, the most studied of these structures, the gravitational field of a monopole exhibits some interesting properties, particularly those concerning the appearance of nontrivial space-time topologies. The solutions corresponding to the metrics generated by strings [2], domain walls [2] and global monopoles [3] in the context of General Relativity were all first obtained using the weak field approximation. In a similar approach, the gravitational fields of cosmic strings and domain walls have been obtained regarding Brans-Dicke theory of gravity and more general scalar-tensor theories of gravity [4, 5]. In this paper we consider the global monopole and investigate its gravitational field by working out Brans-Dicke equations using once more the weak field approximation, essentially in the same way as in the previous works mentioned above. Let us consider Brans-Dicke field equations in the form Rμν = 8π φ [ Tμν − gμν 2 ( 2ω + 2 2ω + 3 )