Abstract:
The exploration of stability or instability range in modified theories provide
deep insight of gravitational interaction in current era which is based on the ex pansion of the universe. In this thesis, we have analyzed cylindrically symmet ric self-gravitating objects for stability analysis within the framework of f(R, T)
gravity. This alternative theory provides substitute to dark energy (DE) which
assumes high negative pressure and is considered to be responsible for cosmic
expansion.
In this discussion, we have considered cylindrically symmetric systems with
anisotropic matter distribution. The modified field equations and dynamical
equations are constructed in f(R, T) theory of gravity. First order perturbation
is applied on the modified field equations and dynamical equations which facil itates the construction of the collapse equation. Instability ranges are explored
in both Newtonian (N) and post-Newtonian (pN) eras with the help of adiabetic
index Γ which measures the pressure variation with changing energy density.
Some conditions are imposed on material variables that are required for stable
configuration.
Cylindrically symmetric sources evolving under expansion-free condition are
analyzed with locally anisotropic distribution . The collapse equation of cylin drical star is obtained by adopting perturbation approach for general solutions
of gravitational field equations and conservation equations. Dynamical insta bility is discussed in N and pN regimes, stability constraints have also been
ixdeveloped. The adiabatic index ‘Γ’ is found to be meaningless for the discus sion of stability of gravitating sources carrying expansion-free condition, while
stability variations are determined by physical properties of the fluid. Stability
analysis for shearing viscous anisotropic fluid with cylindrical symmetry has
also been made in f(R, T) theory
