Dark stars in Starobinsky’s model

Panotopoulos, Grigoris; Lopes, Ilídio

doi:10.1103/physrevd.97.024025

Cited by 23 publications

(15 citation statements)

References 95 publications

(116 reference statements)

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“…Only for sufficiently heavy stars, M ≥ 125 M ⊙ , the Gauss-Bonnet parameter starts to have a considerable impact on the profiles. Similar results were obtained in the four-dimensional Starobinsky model [66,67].…”

Section: Numerical Resultssupporting

confidence: 85%

Relativistic strange quark stars in Lovelock gravity

Panotopoulos

Rincón

2019

Eur. Phys. J. Plus

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We study relativistic non-rotating stars in the framework of Lovelock gravity. In particular, we consider the Gauss-Bonnet term in a five-dimensional spacetime, and we investigate the impact of the Gauss-Bonnet parameter on properties of the stars, both isotropic and anisotropic. For matter inside the star, we assume a relativistic gas of de-confined massless quarks. We integrate the modified Tolman-Oppenheimer-Volkoff equations numerically, and we obtain the mass-to-radius profile, the compactness of the star as well as the gravitational red-shift for several values of the Gauss-Bonnet parameter. The maximum star mass and radius are also reported. PACS. XX.XX.XX No PACS code given 1 IntroductionAlthough our observable Universe is clearly four-dimensional, the question "How many dimensions are there?" is one of the fundamental questions High Energy Physics tries to answer. Kaluza-Klein theories [1,2], supergravity [3] and Superstring/M-Theory [4,5] have pushed forward the idea that extra spatial dimensions may exist. In more than four dimensions higher order curvature terms are natural in Lovelock theory [6], and also higher order curvature corrections appear in the low-energy effective equations of Superstring Theory [7].The amount of published works in the literature reveals that Lovelock gravity is an exciting and active field. Black hole physics [8][9][10][11][12][13][14], cosmological solutions [15][16][17][18] and holographic superconductors exploiting the gauge/gravity duality [19] are some of the areas that have been explored in the framework of Lovelock gravity. However, the astrophysical implications of Lovelock theory should also be investigated. Compact objects [20][21][22], such as white dwarfs and neutron stars, are the final fate of stars, and comprise excellent cosmic laboratories to study, test and constrain new physics and/or alternative theories of gravity under extreme conditions that cannot be reached in Earth-based experiments. It is well-known that the properties of compact objects, such as mass and radius, depend both on the equation-of-state (EoS) of ultra-dense matter and on the underlying theory of gravity.A couple of years after the discovery of the neutron by James Chadwick [23,24], neutron stars were predicted to exist by Baade and Zwicky [25]. Indeed, several decades after that, the discoveries of pulsars in the Crab and Vela supernova remnants [26] led to their identification as neutron stars just one year after the discovery of pulsars in 1967 [27]. On the other hand quark matter is by assumption absolutely stable, and as such it may be the true ground state of hadronic matter [28,29]. Therefore a new class of hypothetical compact objects has been postulated to exist. These compact objects could serve as an alternative to neutron stars, and they might offer us a plausible explanation of the puzzling observation of some super-luminous supernovae [30,31], which occur in about one out of every 1000 supernovae explosions, and which are more than 100 times more luminous than regular su...

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Section: Numerical Resultssupporting

confidence: 85%

Relativistic strange quark stars in Lovelock gravity

Panotopoulos

Rincón

2019

Eur. Phys. J. Plus

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“…From this Eqn. (23) we observe that when = 0, the Hamiltonians become ill-defined, which signifies the necessity of having near-null coordinates to construct the Hamiltonians. Using Hamilton's equation, the field momentum Π can be expressed as…”

Section: Field Hamiltonianmentioning

confidence: 99%

“…The greybody factor is obtained from the transmission amplitude as the field modes pass from near horizon region to an asymptotic observer through the effective potential, created due to the spacetime geometry. Estimation of this greybody factor is a very difficult job and often utilises various approximations like evaluating the greybody factors particularly in asymptotically low or high frequency regimes [15][16][17][18][19][20][21][22][23]. Sometimes, one is forced to take the extremal limit to evaluate these quantities [24][25][26].…”

Section: Introductionmentioning

confidence: 99%

The Hawking effect and the bounds on greybody factor for higher dimensional Schwarzschild black holes

Barman

2020

Eur. Phys. J. C

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In this work, we have considered a n−dimensional Schwarzschild-Tangherlini black hole spacetime with massless minimally coupled free scalar fields in its bulk and 3−brane. The bulk scalar field equation is separable using the higher dimensional spherical harmonics on (n − 2)−sphere. First, using the Hamiltonian formulation with the help of the recently introduced near-null coordinates we have obtained the expected temperature of the Hawking effect, identical for both bulk and brane localized scalar fields. Second, it is known that the spectrum of the Hawking effect as seen at asymptotic future does not correspond to a perfect black body and it is properly represented by a greybody distribution. We have calculated the bounds on this greybody factor for the scalar field in both bulk and 3−brane. Furthermore, we have shown that these bounds predict a decrease in the greybody factor as the spacetime dimensionality n increases and suggest that for a large number of extra dimensions the Hawking quanta is mostly emitted in the brane.

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“…In particular, α r corresponds to the most right value of α and the pair (α t , β t ) stands for coordinates of the top of the shadow [60]. With all the quantities defined in this section, the emission rate [56,[61][62][63][64][65][66][67] can be calculated by…”

Section: Hawking Temperature and Emission Rate Of A Rotating Blacmentioning

confidence: 99%

Black hole shadow of a rotating polytropic black hole by the Newman–Janis algorithm without complexification

et al. 2019

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In this work, starting from a spherically symmetric polytropic black hole, a rotating solution is obtained by following the Newman-Janis algorithm without complexification. Besides studying the horizon, the static conditions and causality issues of the rotating solution, we obtain and discuss the shape of its shadow. Some other physical features as the Hawking temperature and emission rate of the rotating polytropic black hole solution are also discussed.

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Dark stars in Starobinsky’s model

Cited by 23 publications

References 95 publications

Relativistic strange quark stars in Lovelock gravity

Relativistic strange quark stars in Lovelock gravity

The Hawking effect and the bounds on greybody factor for higher dimensional Schwarzschild black holes

Black hole shadow of a rotating polytropic black hole by the Newman–Janis algorithm without complexification

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