A Dynamic Analysis of Cosmic Strings in the $f(R,T)$ Gravity Model

This study investigates the dynamics of cosmic strings within the framework of the $f(R,T)$ gravity model, a modified theory of gravity proposed by Harko et al. in 2011. The $f(R,T)$ theory extends Einstein’s general relativity by including functions of the Ricci scalar ($R$) and the trace of the energy-momentum tensor ($T$). Using the Friedman-Robertson-Walker (FRW) universe model, the study derives the field equations and explores the behavior of the key cosmological parameters, such as the scale factor, string energy density, cosmological term, deceleration parameter, and Hubble parameter. The analytical solutions show that the universe expands continuously with the increasing scale factor values. The study also demonstrates that energy density and the cosmological term decrease over time, while the Hubble parameter exhibits a similar declining trend. The results indicate that the model aligns well with the observed accelerated expansion of the current universe. These findings provide valuable insights into the role of cosmic strings and modified gravity theories in explaining large-scale cosmic evolution.