Abelian cosmic string in the extended Starobinsky model of gravity

TL;DR

This paper investigates how extending the Starobinsky gravity model with additional R^m terms affects the properties of Abelian cosmic strings, revealing that the angular deficit decreases and the cosmic horizon size varies with model parameters.

Contribution

It introduces a numerical analysis of Abelian cosmic strings within an extended f(R) gravity framework, highlighting the impact of higher-order curvature terms on string properties.

Findings

Angular deficit decreases with increasing ta and ta.

Cosmic horizon size varies depending on scalar field VEV and cosmological constant.

Higher-order curvature terms influence cosmic string characteristics.

Abstract

We analyze numerically the behaviour of the solutions corresponding to an Abelian cosmic string taking into account an extension of the Starobinsky model, where the action of general relativity is replaced by $f(R) = R - 2\Lambda + \eta R^2 + \rho R^m$, with $m > 2$. As an interesting result, we find that the angular deficit which characterizes the cosmic string decreases as the parameters $\eta$ and $\rho$ increase. We also find that the cosmic horizon due to the presence of a cosmological constant is affected in such a way that it can grows or shrinks, depending on the vacuum expectation value of the scalar field and on the value of the cosmological constant