Dark energy stars: Stable configurations

Bhar, Piyali; Manna, Tuhina; Rahaman, Farook; Banerjee, Ayan

doi:10.1139/cjp-2017-0526

Cited by 16 publications

(12 citation statements)

References 43 publications

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“…We build our dark energy core by adding matter to its surface without changing its density so as to satisfy the WEC (25). Indeed, in the dark energy core, where p r = p T = −ρ, Eq.…”

Section: Pileup Modelsmentioning

confidence: 99%

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Formation of dark energy stars

Beltracchi

Gondolo

2019

Phys. Rev. D

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Dark energy stars are finite size astrophysical objects with an interior equation of state typical of dark energy. Examples are self-gravitating false vacuum bubbles, vacuum nonsingular black holes, and gravastars. We present a time-dependent solution of Einstein's field equations that describes the collapse of a spherical system from an initial state of positive pressure to a final state with a dark energy core. Our solution has no singularities, no event horizons, and does not violate the weak or null energy conditions. I. INTRODUCTIONThere are various studies of compact astrophysical objects in the interior of which the energy density ρ and the pressure p obey an equation of state typical of dark energy such as p = −ρ. Such objects have been variously named in the literature. We refer to them as "dark energy stars" for simplicity.Although dark energy stars could have spacetime singularities, one is commonly interested in dark energy stars that are nonsingular. Buchdahl's theorem [1] precludes the existence of nonsingular compact objects with radius smaller than 9/8 the Schwarzschild radius under the assumptions of spherical symmetry, isotropic stress, and nonnegative trace of the energy momentum tensor. Compact nonsingular dark energy stars are possible because the nonnegative trace condition does not apply for p < −ρ/3 dark energy (compact objects supported by anisotropy instead have also been studied [2]).In the mid 1960s the idea of objects with p = −ρ at their center was put forward by Gliner [3]. The first concrete solution was the Bardeen spacetime [4][5][6][7], which is a nonsingular, asymptotically flat, spherically symmetric spacetime that may have zero, one, or two event horizons depending on the value of a parameter. The Bardeen stress energy tensor features radial pressure p r = −ρ everywhere and tangential pressure p T = p r away from the center.In the 1980s the gravitational effects of false vacuum bubbles forming in true vacuum, and vice versa, were considered [8]. False-vacuum bubbles were studied as a possibility for wormholes [9] and localized inflation [10,11] when it was found that the null energy condition imposes that any spherically symmetric false-vacuum bubble that forms in an asymptotically flat space, and grows beyond a certain critical size, must have emerged from an initial singularity [11]. Smaller false vacuum bubbles may arise without initial singularities [12]. There were also attempts to replace the black hole singularity inside the horizon with a Planckian density vacuum bubble and a junction layer [13][14][15].Starting in the 1990s, compact objects with p = −ρ at their center, called vacuum nonsingular black holes, or lambda black holes [16][17][18][19], were studied within the class of "regular black-hole" solutions, i.e., asymptotically flat spacetimes that, like black holes, possess an event horizon but, unlike black holes, do not have a singularity (see, e.g., Ref.[20] for a review). Lambda black holes, and similar horizonless objects known as G lumps [21][22][23], are s...

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“…We build our dark energy core by adding matter to its surface without changing its density so as to satisfy the WEC (25). Indeed, in the dark energy core, where p r = p T = −ρ, Eq.…”

Section: Pileup Modelsmentioning

confidence: 99%

“…2. Equation (25) Note that within the normal region ρ and p r are nonnegative, but the inequality from Eq. (25) can still be violated if S r is too high.…”

Section: Equation (24)mentioning

confidence: 99%

Formation of dark energy stars

Beltracchi

Gondolo

2019

Phys. Rev. D

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“…Recent treatments of anisotropic DE stars are to be found in [17], [18] and [19]. In all these cases analytic solutions are given by supplying some functions and constants as external input.…”

Section: Dark Energy Starsmentioning

confidence: 99%

“…In [18] two equations of state and an analytic expression for the DE energy density are given. An analytic expression for the mass function and a DE-equation of state for the radial pressure are provided in [19].…”

Section: Dark Energy Starsmentioning

confidence: 99%

Anisotropic Geodesic Fluid in Non-Comoving Spherical Coordinates

Stichel¹

2018

JMP

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We start with a recently introduced spherically symmetric geodesic fluid model (arXiv: 1601.07030) whose energy-momentum tensor (EMT) in the comoving frame is dust-like with nontrivial energy flux. In the non-comoving energy frame (vanishing energy flux), the same EMT contains besides dust only radial pressure. We present Einstein's equations together with the matter equations in static spherically symmetric coordinates. These equations are self-contained (four equations for four unknowns). We solve them analytically except for a resulting nonlinear ordinary differential equation (ODE) for the gravitational potential. This ODE can be rewritten as a Lienard differential equation which, however, may be transformed into a rational Abel differential equation of the first kind. Finally, we list some open mathematical problems and outline possible physical applications (galactic halos, dark energy stars) and related open problems.

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“…[47][48][49][50][51] to construct compact and static star-like solutions, known as the "dark energy stars", made up of a dark energy fluid. This corresponds to the assumption that in the vicinity of a structure or central mass, the dark energy becomes inhomogeneous too.…”

Section: R Tamax In the Static Geometrymentioning

confidence: 99%

Cosmic structure sizes in generic dark energy models

Bhattacharya

Tomaras

2017

Eur. Phys. J. C

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The maximum allowable size of a spherical cosmic structure as a function of its mass is determined by the maximum turn around radius R TA,max , the distance from its center where the attraction on a radial test particle due to the spherical mass is balanced with the repulsion due to the ambient dark energy. In this work, we extend the existing results in several directions. (a) We first show that, for w = −1, the expression for R TA,max found earlier, using the cosmological perturbation theory, can be derived using a static geometry as well. (b) In the generic dark energy model with arbitrary time dependent state parameter w(t), taking into account the effect of inhomogeneities upon the dark energy as well, it is shown that the data constrain w(t = today) > −2.3. (c) We address the quintessence and the generalized Chaplygin gas models, both of which are shown to predict structure sizes consistent with observations.

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Dark energy stars: Stable configurations

Cited by 16 publications

References 43 publications

Formation of dark energy stars

Formation of dark energy stars

Anisotropic Geodesic Fluid in Non-Comoving Spherical Coordinates

Cosmic structure sizes in generic dark energy models

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