PPNformalism
PPN formalism is a theoretical framework in general relativity and cosmology that combines aspects of the Einstein field equations with the principles of the Perfect Fluid (PF) model. Developed primarily in the mid-20th century, it serves as a simplified yet physically meaningful approximation for describing the large-scale structure of the universe, particularly in homogeneous and isotropic cosmological models.
The formalism is rooted in the assumption that matter in the universe behaves as a perfect fluid,
The PPN parameters are a set of dimensionless coefficients that quantify deviations from general relativity in
In cosmology, PPN formalism is often applied to study the early universe, structure formation, and the behavior