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Register a new userGravastars with Dark Energy Evolving to Naked Singularity
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We consider a gravastar model made of anisotropic dark energy with an infinitely thin spherical shell of a perfect fluid with the equation of state $p = (1-gamma)sigma$ with an external de Sitter-Schwarzschild region. It is found that in some cases the models represent the bounded excursion stable gravastars, where the thin shell is oscillating between two finite radii, while in other cases they collapse until the formation of black holes or naked singularities. An interesting result is that we can have black hole and stable gravastar formation even with an interior and a shell constituted of dark and repulsive dark energy, as also shown in previous work. Besides, in three cases we have a dynamical evolution to a black hole (for $Lambda=0$) or to a naked singularity (for $Lambda > 0$). This is the first time in the literature that a naked singularity emerges from a gravastar model.
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We consider a gravastar model made of anisotropic dark energy with an infinitely thin spherical shell of a perfect fluid with the equation of state $p = (1-gamma)sigma$ with an external de Sitter-Schwarzschild region. It is found that in some cases the models represent the bounded excursion stable gravastars, where the thin shell is oscillating between two finite radii, while in other cases they collapse until the formation of black holes or naked singularities. An interesting result is that we can have black hole and stable gravastar formation even with an interior and a shell cons tituted of dark and repulsive dark energy, as also shown in previous work. Besides, in one case we have a dynamical evolution to a black hole (for $Lambda =0$) or to a naked singularity (for $Lambda > 0$). This is the first time in the literature that a naked singularity emerges from a gravastar model.
We explore the collision between two concentric spherical thin shells. The inner shell is charged, whereas the outer one is either neutral or charged. In the situation we consider, the charge of the inner shell is larger than its gravitational mass, and the inside of it is empty and regular. Hence the domain just outside it is described by the overcharged Reissner-Nordstrom geometry whereas the inside of it is Minkowski. First, the inner shell starts to shrink form infinity with finite kinetic energy, and then the outer shell starts to shrink from infinity with vanishing kinetic energy. The inner shell bounces on the potential wall and collides with the ingoing outer shell. The energy of collision between these shells at their center of mass frame does not exceed the total energy of the system. By contrast, by virtue of the very large gamma factor of the relative velocity of the shells, the energy of collision between two of the constituent particles of these shells at their center of mass frame can be much larger than the Planck scale. This result suggests that the black hole or naked singularity is not necessary for ultra-high energy collision of particles.
Considering the evolution of a perfect fluid with self-similarity of the second kind, we have found that an initial naked singularity can be trapped by an event horizon due to collapsing matter. The fluid moves along time-like geodesics with a self-similar parameter $alpha = -3$. Since the metric obtained is not asymptotically flat, we match the spacetime of the fluid with a Schwarzschild spacetime. All the energy conditions are fulfilled until the naked singularity.
It is now theoretically well established that not only a black hole can cast shadow, but other compact objects such as naked singularities, gravastar or boson stars can also cast shadows. An intriguing fact that has emerged is that the event horizon and the photon sphere are not necessary for a shadow to form. Now, when two different types of equally massive compact objects cast shadows of same size, then it would be very difficult to distinguish them from each other. However, the nature of the nulllike and timelike geodesics around the two compact objects would be different, since their spacetime geometries are different. Therefore, the intensity distribution of light emitted by the accreting matter around the compact objects would also be different. In this paper, we emphasize this phenomenon in detail. Here, we show that a naked singularity spacetime, namely, the first type of Joshi-Malafarina-Narayan (JMN1) spacetime can be distinguishable from the Schwarzschild blackhole spacetime by the intensity distribution of light, though they have same mass and shadow size. We also use the image processing techniques here to show this difference, where we use the theoretical intensity data. The differences that we get by using the image processing technique may be treated as a theoretical template of intensity differences, which may be useful to analyse the observational data of the image of a compact object.
In this paper, we considered the gravitational collapse of a symmetric radiating star consisting of perfect fluid (baryonic) in the background of dark energy (DE) with general equation of state. The effect of DE on the singularity formation has been discussed first separately (only DE present) and then combination of both baryonic and DE interaction. We have also showed that DE components play important role in the formation of Black-Hole(BH). In some cases the collapse of radiating star leads to black hole formation and in other cases it forms Naked-Singularity(or, eternally collapse). The present work is in itself remarkable to describe the effect of dark energy on singularity formation in radiating star.
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