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Paper IPM / Astronomy / 16661  


Abstract:  
The DvaliGabadadzePorrati (DGP) braneworld model is employed to study the gravitational collapse of dust, with a GaussBonnet (GB) term present in the fivedimensional bulk. We find that, within the normal (nonselfaccelerating) 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 latetime 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 inducedgravity 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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