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Abstract Cosmological Black Holes as Models of Cosmological Inhomogeneities
, 2006
"... Since cosmological black holes modify the density and pressure of the surrounding universe, and introduce heat conduction, they produce simple models of cosmological inhomogeneities that can be used to study the eect of inhomogeneities on the universe's expansion. In this thesis, new cosmologi ..."
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cosmological black hole solutions are obtained by generalizing the expanding KerrSchild cosmological black holes to obtain the charged case, by performing a KerrSchild transformation of the Einsteinde Sitter universe (instead of a closed universe) to obtain nonexpanding KerrSchild cosmological black
Kenichi Nakao,
, 2006
"... If expanding and contracting regions coexist in the universe, the speed of the cosmic volume expansion can be accelerated. We construct simple inhomogeneous dustfilled universe models in which the speed of the cosmic volume expansion is accelerated for finite periods. These models are constructed b ..."
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by removing spherical domains from the Einsteinde Sitter universe and filling each domain with a LemaîtreTolmanBondi dust sphere possessing the same gravitational mass as the removed region. This represents an exact solution of the Einstein equations. We find that acceleration of the cosmic volume
Can Inhomogeneities Accelerate the Cosmic Volume
, 2006
"... If expanding and contracting regions coexist in the universe, the speed of the cosmic volume expansion can be accelerated. We construct simple inhomogeneous dustfilled universe models in which the speed of the cosmic volume expansion is accelerated for finite periods. These models are constructed ..."
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by removing spherical domains from the Einsteinde Sitter universe and filling each domain with a LemâıtreTolmanBondi dust sphere possessing the same gravitational mass as the removed region. This represents an exact solution of the Einstein equations. We find that acceleration of the cosmic volume
THE EXTRAGALACTIC DISTANCE SCALE
"... Cepheid variables are used to derive a Virgo cluster distance of 16.0 ± 1.5 Mpc. In conjunction with the Coma velocity and the wellestablished1 Coma/Virgo distance ratio, this yields a Hubble parameter H o = 81 ± 8 km s1 Mpc. By combining this value with an age of the Universe / 16.8 ± 2.1 Gyr, t ..."
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, that is derived from the metalpoor globular cluster M92, one obtains f (S, 7) / 1.39 ± 0.22. This value is only marginally consistent with an Einsteinde Sitter universe with S = 0 and 7 = 0, which has f = 1. An Einsteinde Sitter universe with S = 1 and 7 = 0, for which f = b, appears to be excluded at the 3F
The Evolution of Galactic Disks
, 1997
"... Accepted........ Received.......; in original form....... We use recent observations of highredshift galaxies to study the evolution of galactic disks over the redshift range 0 < z < ∼ 1. The data are inconsistent with models in which disks were already assembled at z = 1 and have evolved onl ..."
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only in luminosity since that time. Assuming that disk properties change with redshift as powers of 1 + z and analysing the observations assuming an Einsteinde Sitter universe, we find that for given rotation speed, disk scalelength decreases with z as ∼ (1 + z) −1, total Bband masstolight ratio
Shear–Free Gravitational Waves in an Anisotropic Universe
, 2002
"... We study gravitational waves propagating through an anisotropic Bianchi I dust–filled universe (containing the Einstein–de–Sitter universe as a special case). The waves are modeled as small perturbations of this background cosmological model and we choose a family of null hypersurfaces in this space ..."
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We study gravitational waves propagating through an anisotropic Bianchi I dust–filled universe (containing the Einstein–de–Sitter universe as a special case). The waves are modeled as small perturbations of this background cosmological model and we choose a family of null hypersurfaces
Evolution of Scaleinvariant Inhomogeneities in Standard Cosmology
, 1997
"... It is shown that density fluctuations obey a scaling law in an open Friedmann universe. In a flat universe, the fluctuations are not scaleinvariant. We compute the growth rate of adiabatic scaleinvariant density fluctuations in flat, open and inflationary universes. We find that, given a sufficien ..."
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sufficiently long time, the density perturbations decay away in the EinsteindeSitter universe. On the contrary, the rapid growth of the density instabilities makes an open universe inhomogeneous in a time scale comparable to the age of our universe. We also find that the fluctuations grow exponentially in a
Towards an accurate determination of the age of the universe
 In Proceedings of the second International Conference on Dark Matter in Astrophysics and Particle Physics
, 1999
"... In the past 40 years a considerable effort has been focused in determining the age of the Universe at zero redshift using several stellar clocks. In this review I will describe the best theoretical methods to determine the age of the oldest Galactic Globular Clusters (GC). I will also argue that a m ..."
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Cited by 1 (0 self)
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for the oldest GCs is 10.5 Gyr and the maximum is 16.0 Gyr (with 99 % confidence). Therefore, an EinsteinDe Sitter Universe (Ω = 1) is not totally ruled out if the Hubble constant is about 65 ± 10 km s −1 Mpc −1. On the other hand, the newly discovered red elliptical 53W069 (z = 1.43) provides an stronger
The Bianchi classification of maximal D = 8 gauged supergravities
"... We perform the generalized dimensional reduction of D = 11 supergravity over threedimensional group manifolds as classified by Bianchi. Thus, we construct 11 different maximal D = 8 gauged supergravities, two of which have an additional parameter. One class of group manifolds (class B) leads to sup ..."
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Cited by 21 (9 self)
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reduction gives the Einstein–de Sitter universe in D = 4. The uplifting of the different solutions to Mtheory and the isometries of the corresponding group manifold are discussed. PACS numbers: 04.50.+h, 04.65.+e, 11.25.−w 1.
Results 11  20
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