“School of Astronomy”
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| Paper IPM / Astronomy / 16661 |
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The Dvali-Gabadadze-Porrati (DGP) braneworld model is employed to study the gravitational collapse of dust, with a Gauss-Bonnet (GB) term present in the five-dimensional bulk. We find that, within the normal (nonself-accelerating) DGP branch and due to the curvature effects from the GB component on the brane, the black hole singularity acquires modified features. More precisely, during collapse and for a finite comoving time, before a singularity would emerge at the zero physical radius, the first time derivative of the Hubble rate diverges, whereas the brane energy density and the Hubble rate remain finite. This is a peculiar behavior which displays similar properties to the sudden singularity occurring in particular late-time cosmological frameworks. Furthermore, the question of whether this altered singularity can be viewed by an external observer or will be hidden by a black hole horizon is addressed. We establish that, depending on the given induced-gravity parameter and the GB coupling constant, there exists a {\em threshold mass} for the collapsing dust, below which no trapped surfaces evolve as the collapse proceeds toward the singularity. In other words, a {\em naked sudden singularity} may form.
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