Cavity Evolution and Instability Constraints of Relativistic Interiors
  In this manuscript, we have identified the dynamical instability constraints of a self-gravitating cylindrical object within the framework of $f(R,T)$ theory of gravity. We have explored the modified field equations and corresponding dynamical equations for the systematic constructions of our analysis. We have imposed the linear perturbations on metric and material variables with some known static profile up to first order in the perturbation parameter. The role of expansion scalar is also examined in this scenario. The instability regimes have been discussed in the background of Newtonian and post-Newtonian limits. We found that the dark source terms due to the influence of modification in the gravity model is responsible for the instability of the system. 
Z. Yousaf and M. Zaeem ul Haq Bhatti
physics.gen-ph