A new f(R) Gravity Model and properties of Gravitational Waves in it

TL;DR

This paper introduces a new $f(R)$ gravity model with enhanced parametric control, explores its gravitational wave properties, and demonstrates its consistency with observational data and potential to address astrophysical and cosmological issues.

Contribution

The paper presents a novel $f(R)$ gravity model with detailed analysis of gravitational wave polarizations and constraints, expanding the understanding of modified gravity theories.

Findings

Existence of scalar polarization modes in the model.

Longitudinal mode travels slower than tensor modes.

Model passes solar system tests and aligns with pulsar timing data.

Abstract

In this paper, we have introduced a new $f(R)$ gravity model as an attempt to have a model with more parametric control, so that the model can be used to explain the existing problems as well as to explore new directions in physics of gravity, by properly constraining it with recent observational data. Here basic aim is to study the properties of Gravitational Waves (GWs) in this new model. In $f(R)$ gravity metric formalism, the model shows the existence of scalar degree of freedom as like other $f(R)$ gravity models. Due to this reason, there is a scalar mode of polarization of GWs present in the theory. This polarization mode exists in a mixed state, of which one is transverse massless breathing mode with non-vanishing trace and the other is massive longitudinal mode. The longitudinal mode being massive, travels at speed less than the usual tensor modes found in General Relativity (GR). Moreover, for a better understanding of the model, we have studied the potential and mass of scalar graviton in both Jordan frame and Einstein frame. This model can pass the solar system tests and can explain primordial and present dark energy. Also, we have put constraints on the model. It is found that the correlation function for the third mode of polarization under certain mass scale predicted by the model agrees well with the recent data of Pulsar Timing Arrays. It seems that this new model would be useful in dealing with different existing issues in the areas of astrophysics and cosmology.