Instability Analysis of Cylindrical Stellar Object in Brans-Dicke Gravity

TL;DR

This study analyzes the stability of cylindrically symmetric stellar objects in Brans-Dicke gravity, revealing how instability depends on fluid properties and the adiabatic index in different gravitational regimes.

Contribution

It introduces a perturbation-based method to determine instability ranges in Brans-Dicke gravity for both isotropic and anisotropic fluids.

Findings

System is always unstable for 0<Γ<1.

Stability depends on dynamical variables of the fluid.

Instability for Γ>1 occurs only in special cases.

Abstract

This paper investigates instability ranges of a cylindrically symmetric collapsing stellar object in Brans-Dicke theory of gravity. For this purpose, we use perturbation approach in the modified field equations as well as dynamical equations and construct a collapse equation. The collapse equation with adiabatic index ($\Gamma$) is used to explore the instability ranges of both isotropic as well as anisotropic fluid in Newtonian and post-Newtonian approximations. It turns out that the instability ranges depend on the dynamical variables of collapsing fluid. We conclude that the system always remains unstable for $0<\Gamma<1$ while $\Gamma>1$ provides instability only for the special case.