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Browsing by Author "Malafarina, D."

Browsing by Author "Malafarina, D."

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  • All black holes in Lemaˆıtre-Tolman-Bondi inhomogeneous dust collapse 
    Joshi, Pankaj S.; Malafarina, D. (2015-09-08)
    Within the Lemaˆıtre-Tolman-Bondi formalism for gravitational collapse of inhomogeneous dust we analyze the parameter space that leads to the formation of a globally covered singularity (i.e. a black hole) when some ...
  • Can we observationally test the weak cosmic censorship conjecture? 
    Kong, Lingyao; Malafarina, D.; Bambi, Cosimo (2014-08-04)
    In general relativity, gravitational collapse of matter fields ends with the formation of a spacetime singularity, where the matter density becomes infinite and standard physics breaks down. According to the weak cosmic ...
  • Circular geodesics and accretion disks in Janis-Newman-Winicour and Gamma metric 
    Chowdhury, Anirban N.; Patil, Mandar; Malafarina, D.; Joshi, Pankaj S. (2012-04-19)
    We study here circular timelike geodesics in the Janis-Newman-Winicour and Gamma metric spacetimes which contain a strong curvature naked singularity and reduce to the Schwarzschild metric for a specific value of one of ...
  • Compact objects from gravitational collapse: an analytical toy model 
    Malafarina, D.; Joshi, Pankaj S. (2015)
    We develop here a procedure to obtain regular static configurations as resulting from dynamical gravitational collapse of a massive matter cloud in general relativity. Under certain general physical assumptions for the ...
  • Distinguishing black holes from naked singularities through their accretion disk properties 
    Joshi, Pankaj S.; Malafarina, D.; Narayan, Ramesh (2014-05-06)
    We show that, in principle, a slowly evolving gravitationally collapsing perfect fluid cloud can asymptotically settle to a static spherically symmetric equilibrium configuration with a naked singularity at the center. We ...
  • Equilibrium configurations from gravitational collapse 
    Joshi, Pankaj S.; Narayan, Ramesh; Malafarina, D. (2011-11-18)
    We develop here a new procedure within Einstein’s theory of gravity to generate equilibrium configurations that result as the final state of gravitational collapse from regular initial conditions. As a simplification, we ...
  • Genericity aspects in gravitational collapse to black holes and naked singularities 
    Joshi, Pankaj S.; Malafarina, D.; Saraykar, Ravindra V. (2012-07-04)
    We investigate here the genericity and stability aspects for naked singularities and black holes that arise as the final states for a complete gravitational collapse of a spherical massive matter cloud. The form of the ...
  • Gravitational blueshift from a collapsing object 
    Kong, Lingyao; Malafarina, D.; Bambi, Cosimo (2014-12-22)
    We discuss a counterintuitive phenomenon of classical general relativity, in which a significant fraction of the radiation emitted by a collapsing object and detected by a distant observer may be blueshifted rather than ...
  • Gravitational Collapse of Inhomogenous Perfect Fluid 
    Satin, Seema; Malafarina, D.; Joshi, Pankaj S. (2014)
    We study the complete gravitational collapse of a class of inhomogeneous perfect fluid models obtained by introducing small radial perturbations in an otherwise homogeneous matter cloud. The key feature that we assume for ...
  • Gravitational collapse with tangential pressure 
    Malafarina, D.; Joshi, Pankaj S. (2011-05-06)
    Using the general formalism for spherical gravitational collapse developed in [1], we investigate here the final fate of a spherical distribution of a matter cloud, where radial pressures vanish but tangential pressures ...
  • Instability of black hole formation under small pressure perturbations 
    Joshi, Pankaj S.; Malafarina, D. (2012-11-14)
    We investigate here the spectrum of gravitational collapse endstates when arbitrarily small perfect fluid pressures are introduced in the classic black hole formation scenario as described by Oppenheimer, Snyder and Datt ...
  • Ka iron line profile from accretion disks around regular and singular exotic compact objects 
    Bambi, Cosimo; Malafarina, D. (2013-09-10)
    The nature of the super-massive black hole candidates in galactic nuclei can be tested by ana-lyzing the profile of the Ka iron line observed in their X-ray spectrum. In this paper, we consider the possibility that the ...
  • Naked Singularities as Particle Accelerators II 
    Patil, Mandar; Joshi, Pankaj S.; Malafarina, D. (2011-02-14)
    We generalize here our earlier results on particle acceleration by naked singularities. We showed recently [1] that the naked singularities that form due to gravitational collapse of massive stars provide a suitable ...
  • Non-singular quantum-inspired gravitational collapse 
    Bambi, Cosimo; Malafarina, D.; Modesto, Leonardo (2013-08-07)
    We consider general relativistic homogeneous gravitational collapses for dust and radiation. We show that replacing the density profile with an effective density justified by some quantum gravity framework leads to the ...
  • Note on the effect of a massive accretion disk in the measurements of black hole spins 
    Bambi, Cosimo; Malafarina, D.; Tsukamoto, Naoki (2014-06-25)
    The spin measurement of black holes has important implications in physics and astrophysics. Regardless of the specific technique to estimate the black hole spin, all the current approaches assume that the space-time geometry ...
  • Recent developments in gravitational collapse and spacetime singularities 
    Joshi, Pankaj S.; Malafarina, D. (2012-01-19)
    It is now known that when a massive star collapses under the force of its own gravity, the final fate of such a continual gravitational collapse will be either a black hole or a naked singularity under a wide variety of ...
  • Scalar field collapse and cosmic censorship 
    Goswami, Rituparno; Joshi, Pankaj S.; Malafarina, D. (2012-02-28)
    We analyze here the final fate of complete gravitational collapse of a massless scalar field within general relativity. A class of dynamical solutions with initial data close to the Friedmann-Lemaˆıtre-Robertson-Walker ...
  • Semiclassical gravitational collapse and avoidance of singularities 
    Malafarina, D. (Nazarbayev University, 2014)
    General Relativity (GR) predicts that, under standard conditions for normal matter, when gravity prevails over other forces, a space-time singularity must form [1]. On the other hand singularities are not expected to ...
  • Singularity avoidance in classical gravity from four-fermion interaction 
    Bambi, Cosimo; Malafarina, D.; Marcian`o, Antonino; Modesto, Leonardo (2014-05-26)
    We derive the dynamics of the gravitational collapse of a homogeneous and spherically symmetric cloud in a classical set-up endowed with a topological sector of gravity and a non-minimal coupling to fermions. The effective ...
  • Singularity avoidance in quantum-inspired inhomogeneous dust collapse 
    Liu, Yue; Malafarina, D.; Modesto, Leonardo; Bambi, Cosimo (2014-08-17)
    In a previous paper, some of us studied general relativistic homogeneous gravitational collapses for dust and radiation, in which the density profile was replaced by an effective density justified by some quantum gravity ...