Cosmic stringlike objects in hybrid metricPalatini gravity
Abstract
We consider static and cylindrically symmetric interior stringtype solutions in the scalartensor representation of the hybrid metricPalatini modified theory of gravity. As a first step in our study, we obtain the gravitational field equations and further simplify the analysis by imposing Lorentz invariance along the t and z axes, which reduces the number of unknown metric tensor components to a single function W^{2}(r ). In this case, the general solution of the field equations can be obtained, for an arbitrary form of the scalar field potential, in an exact closed parametric form, with the scalar field ϕ taken as a parameter. We consider in detail several exact solutions of the field equations, corresponding to a null and constant potential, and to a powerlaw potential of the form V (ϕ )=V_{0}ϕ^{3 /4}, in which the behaviors of the scalar field, of the metric tensor components, and of the string tension can be described in a simple mathematical form. We also investigate the string models with exponential and Higgstype scalar field potentials by using numerical methods. In this way, we obtain a large class of novel stable stringlike solutions in the context of hybrid metricPalatini gravity, in which the basic parameters, such as the scalar field, metric tensor components, and string tension, depend essentially on the initial values of the scalar field, and of its derivative, on the r =0 circular axis.
 Publication:

Physical Review D
 Pub Date:
 June 2020
 DOI:
 10.1103/PhysRevD.101.124050
 arXiv:
 arXiv:2003.09751
 Bibcode:
 2020PhRvD.101l4050H
 Keywords:

 General Relativity and Quantum Cosmology;
 Astrophysics  High Energy Astrophysical Phenomena;
 High Energy Physics  Theory
 EPrint:
 15 pages, 9 figures: V2: slight change in title and abstract