White dwarf stars in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>D</mml:mi></mml:math>dimensions

Chavanis, Pierre‐Henri

doi:10.1103/physrevd.76.023004

Cited by 42 publications

(81 citation statements)

References 46 publications

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“…The condensation temperature for Bose gas as well as the Fermi temperature for Fermi gas should be affected with such NC spacetime. The former case is interesting in the scalar field dark matter model [37], where the dark matter particle is a spin-0 boson, while the latter is important in the case of Chandrashekhar limit [38]. Generalisation of standard cosmology result in this current framework is the next program that we wish to take up.…”

Section: Resultsmentioning

confidence: 99%

On Boundedness of Entropy of Photon Gas in Noncommutative Spacetime

Alam¹,

Faruk²

2017

Advances in High Energy Physics

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Entropy bound for the photon gas in a noncommutative (NC) spacetime where phase space is with compact spatial momentum space, previously studied by Nozari et al., has been reexamined with the correct distribution function. While Nozari et al. have employed Maxwell-Boltzmann distribution function to investigate thermodynamic properties of photon gas, we have employed the correct distribution function, that is, Bose-Einstein distribution function. No such entropy bound is observed if Bose-Einstein distribution is employed to solve the partition function. As a result, the reported analogy between thermodynamics of photon gas in such NC spacetime and Bekenstein-Hawking entropy of black holes should be disregarded.

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Section: Resultsmentioning

confidence: 99%

On Boundedness of Entropy of Photon Gas in Noncommutative Spacetime

Alam¹,

Faruk²

2017

Advances in High Energy Physics

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“…In [62] a complete heuristic study, following the original work of Landau (see, e.g, [64]), was performed. Then in [63], the full study, following the original works of Chandrasekhar (see, e.g, [65]), was completed. The main conclusion is that there are no Newtonian solutions for degenerate stars in higher dimensions, thus no general relativistic solutions also, the Fermi pressure energy cannot balance the gravitational energy.…”

Section: Contextmentioning

confidence: 99%

“…Indeed, interesting papers discussing degenerate stars, like white dwarfs and neutron stars, in higher dimensions have appeared [62,63]. In [62] a complete heuristic study, following the original work of Landau (see, e.g, [64]), was performed.…”

Section: Contextmentioning

confidence: 99%

Bonnor stars indspacetime dimensions

Lemos¹,

Zanchin

2008

Phys. Rev. D

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Bonnor stars are regular static compact configurations in equilibrium, composed of an extremal dust fluid, i.e., a charged dust fluid where the mass density is equal to the charge density in appropriate units and up to a sign, joined to a suitable exterior vacuum solution, both within Newtonian gravity and general relativity.In four dimensions, these configurations obey the Majumdar-Papapetrou system of equations, in one case, the system is a particular setup of Newtonian gravity coupled to Coulomb electricity and electrically charged matter or fluid, in the other case, the system is a particular setup of general relativity coupled to Maxwell electromagnetism and electrically charged matter or fluid, where the corresponding gravitational potential is a specially simple function of the electric potential field and the fluid, when there is one, is made of extremal dust. Since the Majumdar-Papapetrou system can be generalized to d spacetime dimensions, as has been previously done, and higher dimensional scenarios can be important in gravitational physics, it is natural to study this type of Bonnor solutions in higher dimensions, d ≥ 4. As a preparation, we analyze Newton-Coulomb theory with an electrically charged fluid in a Majumdar-Papapetrou context, in d = n + 1 spacetime dimensions, with n being the number of spatial dimensions. We show that within the Newtonian theory, in vacuum, the Majumdar-Papapetrou relation for the gravitational potential in terms of the electric potential, and its related Weyl relation, are equivalent, in contrast with general relativity where they are distinct. We study a class of spherically symmetric Bonnor stars within this theory. Under sufficient compactification they form point mass charged Newtonian singularities. We then study the analogue type systems in the Einstein-Maxwell theory with an electrically charged fluid. Drawing on our previous work on the d-dimensional Majumdar-Papapetrou system, we restate some properties of this system. We obtain spherically symmetric Bonnor star solutions in d = n + 1 spacetime dimensions. We show that these stars, under sufficient compactification, form d-dimensional quasi-black holes. We also show that in the appropriate low gravity limit theses solutions turn into the solutions of Newtonian gravity, i.e., they are quasi-Newtonian Bonnor stars. In this connection, we note that the star solutions in Majumdar-Papapetrou Newtonian gravity, when contrasted to those solutions in Majumdar-Papapetrou general relativity, display clearly the branching off of the high density objects that may arise in the strong field regime of each theory, mild singularities in one theory, quasi-black holes in the other. Another important feature worth of mention is that, whereas there are no solutions for Newtonian or relativistic stars supported by degenerate pressure in higher dimensions, higher dimensional Bonnor stars, supported by electric repulsion, do indeed have solutions within Newtonian gravity and general relativity. So the existence of stars in h...

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“…52; also cf. [55]. The equilibrium state (denoted by subscript '0') is defined by the state "vector" …”

Section: The Modelmentioning

confidence: 99%

Coexistence of negative and positive polarity electrostatic solitary waves in ultradense relativistic negative-ion-beam permeated plasmas

Elkamash

Kourakis

2018

Physics of Plasmas

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The criteria for occurrence and the dynamical features of electrostatic solitary waves in a homogeneous, unmagnetized ultradense plasma penetrated by a negative ion beam are investigated, relying on a quantum hydrodynamic model. The ionic components are modeled as inertial fluids, while the relativistic electrons obey Fermi-Dirac statistics. A new set of exact analytical conditions for localized solitary pulses to exist is obtained, in terms of plasma density. The algebraic analysis reveals that these depend sensitively on the negative ion beam characteristics, that is, the beam velocity and density. Particular attention is paid to the simultaneous occurrence of positive and negative potential pulses, identified by their respective distinct ambipolar electric field structure forms. It is shown that the coexistence of positive and negative potential pulses occurs in a certain interval of parameter values, where the ion beam inertia becomes significant.

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White dwarf stars inDdimensions

Cited by 42 publications

References 46 publications

On Boundedness of Entropy of Photon Gas in Noncommutative Spacetime

On Boundedness of Entropy of Photon Gas in Noncommutative Spacetime

Bonnor stars indspacetime dimensions

Coexistence of negative and positive polarity electrostatic solitary waves in ultradense relativistic negative-ion-beam permeated plasmas

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