Amir Hadi Ziaie, Paulo Vargas Moniz, Arash Ranjbar, Hamid Reza Sepangi
We consider the gravitational collapse of matter, whose content is a Weyssenhoff fluid, in the presence of a negative cosmological constant. Such fluid conveys effects that can be associated to fermionic spin-angular momentum features suitably averaged. Our purpose in this paper is precisely to investigate how those effects may influence the final outcome of the mentioned collapse. For a specific spacetime setup (namely the Tolman-Bondi marginally bound case), we obtain a family of exact solutions to the field equations, which exhibits a spacetime singularity. We further find that, for a specific subset of those solutions, the formation of trapped surfaces can be prevented. Whether a naked singularity emerges or not, this is shown to depend on parameters of the Weyssenhoff fluid, which are related to an averaged spin density as well as to an axial current. The nature of the central singularity is examined and it is shown that null trajectories can emerge from the singularity, exposing it at least to neighboring observers (locally naked singularity). Moreover, by examining the curvature growth along these null trajectories, we show that the singularity can be gravitationally strong, thus providing a counter-example to the cosmic censorship conjecture. Our results respect the regularity of the initial data and also the energy conditions, which are required for the physical reasonableness of the collapsing configuration.
View original:
http://arxiv.org/abs/1305.3085
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