Semi-transparent brane-worlds

Keresztes, Zoltán; Kepiro, Ibolya E.; Gergely, L.

doi:10.1088/1475-7516/2006/05/020

Cited by 7 publications

(4 citation statements)

References 28 publications

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“…Cosmological evolution in this radiation-filled bulk was further exploited in [2]- [10]. The parameters of the model can be fitted in such a way that the late time universe is extremely close to what is predicted by general relativity and verified by astronomical observations.…”

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confidence: 88%

“…Friedmann branes, for example, are known to be embeddible into any of the Schwarzschild / Reissner-Nordström / Vaidya -anti de Sitter bulks (depending on the energy-momentum in the bulk; for a systematic treatment see [3]). Cosmological evolution has been extensively studied in this scenario (for symmetric embeddings see [7], [8] and references therein; for asymmetric embeddings [3], [9] and references therein). The matter in the bulk affects the cosmological evolution on the brane through a "comoving mass" and a bulk pressure [10], [11].…”

Section: Introductionmentioning

confidence: 99%

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Black holes and dark energy from gravitational collapse on the brane

Gergely

2007

J. Cosmol. Astropart. Phys.

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The gravitational collapse of a pressureless fluid in general relativity (Oppenheimer-Snyder collapse) results in a black hole. The study of the same phenomenon in the brane-world scenario has shown that the exterior of the collapsing dust sphere cannot be static. We show that by allowing for pressure, the exterior of a fluid sphere can be static. The gravitational collapse on the brane proceeds according to the modified gravitational dynamics, turning the initial nearly dust-like configuration into a fluid with tension. The tension arises from the non-linearity of the dynamical equations in the energy-momentum tensor, and it vanishes in the general relativistic limit. Below the horizon the tension turns the star into dark energy. This transition occurs right below the horizon for astrophysical black holes and far beyond the horizon for intermediate mass and galactic black holes. Further, both the energy density and the tension increase towards infinite values during the collapse. The infinite tension however could not stop the formation of the singularity.

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confidence: 88%

Section: Introductionmentioning

confidence: 99%

Black holes and dark energy from gravitational collapse on the brane

Gergely

2007

J. Cosmol. Astropart. Phys.

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“…( 49). (All applications to specific models of the formalism derived in [4] were for a brane bounding interior regions [42], [32], [43].) The cases characterized by S L 1 S R 1 = −1 are not incorporated in the present analysis, their discussion in full detail being beyond the scope of the present paper.…”

Section: Discussion and Concluding Remarksmentioning

confidence: 99%

Friedmann branes with variable tension

Gergely

2008

Phys. Rev. D

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We introduce brane-worlds with non-constant tension, strenghtening the analogy with fluid membranes, which exhibit a temperature-dependence according to the empirical law established by E\"otv\"os. This new degree of freedom allows for evolving gravitational and cosmological constants, the latter being a natural candidate for dark energy. We establish the covariant dynamics on a brane with variable tension in full generality, by considering asymmetrically embedded branes and allowing for non-standard model fields in the 5-dimensional space-time. Then we apply the formalism for a perfect fluid on a Friedmann brane, which is embedded in a 5-dimensional charged Vaidya-Anti de Sitter space-time.Comment: 12 pages, to appear in Phys. Rev.

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“…The combined effect of asymmetry and a bulk radiation qualitatively gives both dark matter and dark energy. 53,54 The radiation pressure accelerates the brane, as would dark energy do, while the absorbed radiation increases the energy density of the bulk, appearing as CDM. These two effects compete with each other, and with properly chosen initial data a critical-like behavior can be found.…”

Section: The Dark Matter Session At Berlinmentioning

confidence: 99%

Dark Matter and Sterile Neutrinos

Biermann

Munyaneza

2008

The Eleventh Marcel Grossmann Meeting

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Dark matter has been recognized as an essential part of matter for over 70 years now, and many suggestions have been made, what it could be. Most of these ideas have centered on Cold Dark Matter, particles that are predicted in extensions of standard particle physics, such as supersymmetry. Here we explore the concept that dark matter is sterile neutrinos, particles that are commonly referred to as Warm Dark Matter. Such particles have keV masses, and decay over a very long time, much longer than the Hubble time. In their decay they produce X-ray photons which modify the ionization balance in the very early universe, increasing the fraction of molecular Hydrogen, and thus help early star formation. Sterile neutrinos may also help to understand the baryon-asymmetry, the pulsar kicks, the early growth of black holes, the minimum mass of dwarf spheroidal galaxies, as well as the shape and smoothness of dark matter halos. As soon as all these tests have been made quantitative in their various parameters, we may focus on the creation mechanism of these particles, and could predict the strength of the sharp X-ray emission line, expected from any large dark matter assembly. A measurement of this X-ray emission line would be definitive proof for the existence of may be called weakly interacting neutrinos, or WINs.

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Semi-transparent brane-worlds

Cited by 7 publications

References 28 publications

Black holes and dark energy from gravitational collapse on the brane

Black holes and dark energy from gravitational collapse on the brane

Friedmann branes with variable tension

Dark Matter and Sterile Neutrinos

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