Yazar "Tavakoli, Yaser" seçeneğine göre listele

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    Öğe
    Exploring the cosmic censorship conjecture with a Gauss-Bonnet sector
    (Amer Physical Soc, 2021) Tavakoli, Yaser; Ardabili, Ahad K.; Moniz, Paulo Vargas
    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 threshold mass for the collapsing dust, below which no trapped surfaces evolve as the collapse proceeds toward the singularity. In other words, a naked sudden singularity may form.
  • [ X ]
    Öğe
    Role of Gauss-Bonnet corrections in a DGP brane gravitational collapse
    (2022) Tavakoli, Yaser; Ardabili, Ahad K.; Bouhmadi-Lopez, Mariam; Moniz, Paulo Vargas
    An Oppenheimer-Snyder (OS)-type collapse is considered for a Dvali-Gabadadze-Porrati (DGP) brane, whereas a Gauss-Bonnet (GB) term is provided for the bulk. We study the combined effect of the DGP induced gravity plus the GB curvature, regarding any modification of the general relativistic OS dynamics. Our paper has a twofold objective. On the one hand, we investigate the nature of singularities that may arise at the collapse end state. It is shown that all dynamical scenarios for the contracting brane would end in one of the following cases, depending on conditions imposed: either a central shell-focusing singularity or what we designate as a ???sudden collapse singularity.??? On the other hand, we also study the deviations of the exterior spacetime from the standard Schwarzschild geometry, which emerges in our modified OS scenario. Our purpose is to investigate whether a black hole always forms regarding this brane world model. We find situations where a naked singularity emerges instead.