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Notes on pseudo symmetric and pseudo Ricci symmetric generalized Robertson–Walker space-times

  • Abdallah Abdelhameed Syied,
  • Uday Chand De,
  • Nasser Bin Turki,
  • Gabriel-Eduard Vîlcu

摘要

We establish two key results regarding pseudo symmetric and pseudo Ricci symmetric space-times. Firstly, we demonstrate that in pseudo symmetric generalized Robertson-Walker space-times either the scalar curvature remains constant or the associated vector field \(B_{i}\) B i is irrotational. Secondly, in pseudo Ricci symmetric generalized Robertson-Walker space-times, we establish that either the scalar curvature is zero or the associated vector field \(A_{i}\) A i is irrotational. We identify the conditions to ensure both \(B_{i}\) B i and \(A_{i}\) A i of these manifolds are acceleration-free and vorticity-free. We provide evidence that a pseudo symmetric and pseudo Ricci symmetric GRW space-time can be described as a perfect fluid. In a pseudo symmetric space-time, the state equation is given by \(p=\frac{4-n}{ 2n-2}\mu \) p = 4 - n 2 n - 2 μ , whereas in a pseudo Ricci symmetric space-time, the state equation takes the form \(p=\frac{3-n}{n-1}\mu \) p = 3 - n n - 1 μ , where p and \(\mu \) μ are the isotropic pressure and the energy density. It is noteworthy that if \(n=4\) n = 4 , a pseudo symmetric space-time corresponds to the dust matter era, while a pseudo Ricci symmetric space-time corresponds to the phantom era.