Cosmological axial gravitational waves in the f(R) Starobinsky model

Author(s)

Siddiqa, Aisha ^[1] ; Mehwish, Syeda Z. B. ^[1] ; Alves, Marcio E. S. ^[2]

Affiliation

^[1] Virtual Univ Pakistan, Dept Math, 54 Lawrence Rd, Lahore - Pakistan

^[2] Univ Estadual Paulista UNESP, Inst Ciencia & Tecnol, BR-12247004 Sao Jose Dos Campos, SP - Brazil

• Document type: Journal article
• Source: EUROPEAN PHYSICAL JOURNAL PLUS; v. 136, n. 4 APR 20 2021.
• Web of Science Citations: 1

Abstract

We investigate the propagation of cosmological axial (or odd parity) gravitational waves (GWs) in the framework of the f(R) gravity with f(R)=R+lambda R2, the Starobinsky model. The metric tensor and the energy-momentum tensor of matter are perturbed by using the Regge-Wheeler axial perturbations framework. We solve the coupled system of differential equations of the perturbation parameters for two cosmological eras in which simply analytical solutions can be found, namely the radiation-dominated epoch and the de Sitter stage. In the former case, the Starobinsky model predicts exactly the same result of the General Relativity theory. On the other hand, remembering that in the Starobinsky inflation, the Universe starts within a metastable de Sitter state, we find the evolution of the axial GWs for this early epoch. In this sense, our results should be interpreted as the initial conditions for axial GWs in the Starobinsky model. We show how the initial evolution of axial GWs is affected by the presence of the higher-order curvature term and how it depends on the model parameter lambda. Certainly, such an effect could leave an imprint on the spectrum of axial GWs at the end of the Starobinsky inflation, but this is a subject of further investigations. (AU)

• FAPESP's process: 13/26258-4 - Superdense matter in the universe
• Grantee: Manuel Máximo Bastos Malheiro de Oliveira
• Support Opportunities: Research Projects - Thematic Grants