Interior spacetimes sourced by stationary differentially rotating irrotational cylindrical fluids. II. Axial pressure

TL;DR

This paper develops new exact solutions for interior spacetimes with stationary, differentially rotating irrotational fluids with axial pressure, analyzing their mathematical properties and physical plausibility, and matching them to exterior vacuum solutions.

Contribution

It introduces a general method for generating solutions and classifies three solution types with distinct physical and mathematical features.

Findings

Class C exhibits physically realistic properties.

Class B involves exotic matter with negative energy density.

All classes can be matched to exterior vacuum solutions.

Abstract

In a recent series of papers new exact analytical solutions of Einstein equations representing interior spacetimes sourced by stationary rigidly rotating cylinders of fluids have been displayed. We have first considered a fluid with an axially directed pressure C\'el\'erier, Phys. Rev. D 104, 064040 (2021), J. Math. Phys. 64, 032501 (2023), then a perfect fluid, J. Math. Phys. 64, 022501 (2023), followed by a fluid with an azimuthally directed pressure, J. Math. Phys. 64, 042501 (2023), and finally a fluid where the anisotropic pressure is radially oriented, J. Math. Phys. 64, 052502 (2023). This work is being currently extended to the cases of differentially rotating irrotational fluids. The results are presented in a new series of papers considering, in turn, a perfect fluid source, arXiv:2305.11565 [gr-qc], and the same three anisotropic pressure cases. Here, fluids with an axially directed pressure are considered. A general method for generating new mathematical solutions to the field equations is displayed and three classes are presented so as to exemplify this recipe. Their mathematical and physical properties are analyzed. The first class, named class A, whose other mathematical and physical properties determine a standard configuration, is shown to exhibit a singular axis of symmetry which can be considered as an awkward drawback. The second class, class B, is free from such a singularity but appears to exhibit a negative energy density which characterizes a rather exotic kind of matter. The third class, class C, is the best behaved since it possesses the main properties expected from spacetimes sourced by rather standard fluids. The three classes are matched to an exterior Lewis-Weyl vacuum and the conditions for avoiding an angular deficit are discussed. A comparison with the rigidly rotating fluid case is provided.