Tachyonic field coupled with global monopole in Brans-Dicke theory

Abstract In this paper, we investigate the coupling of a tachyonic field with a global monopole in the framework of the Brans-Dicke modified gravity theory. Global monopoles, formed during the early universe’s phase transitions due to spontaneous symmetry breaking, provide a unique insight into the Universe’s nascent stages. Motivated by earlier works on monopoles and tachyonic fields, we aim to analyse how Brans-Dicke gravity influences global monopoles and their associated tachyonic fields. We derive and solve the field equations under a weak field approximation, considering the effects of the Brans-Dicke parameter ω and the monopole’s scalar field on the resulting spacetime. Additionally, we study the geodesics and bending of light in this modified spacetime both for massless and massive particles. The findings reveal distinct gravitational effects caused by the tachyonic field and global monopole under Brans-Dicke gravity, potentially offering new perspectives on early universe physics and topological defects.