String or branelike solutions in four-dimensional Einstein gravity in the presence of a cosmological constant

Lee, Youngone; Kang, G.; Kim, Hyeong-Chan; Lee, Jungjai

doi:10.1103/physrevd.84.084042

Cited by 4 publications

(5 citation statements)

References 49 publications

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“…As shown in Ref. [13], the geometry is closely connected with the anti-de Sitter black brane solution discovered by Lemos [14]. There are various reasons why this spacetime is a good testing ground in analyzing the properties of anisotropic universes.…”

Section: Introductionmentioning

confidence: 91%

Revisiting the spectrum of a scalar field in an anisotropic universe

Kim

Minamitsuji

2014

Journal of the Korean Physical Society

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We revisit the issue on signatures of pre-inflationary background anisotropy by considering the quantization of a massless and minimally coupled scalar field in an axially symmetric Kasner background, mimicking cosmological perturbations. We show that the power spectrum of the scalar field fluctuation has a negligible difference from the standard inflation in the non-planar directions, but it has a sharp peak around the symmetry plane. For the non-planar high-momentum modes, we use the WKB approximation for the first period and the asymptotic approximation based on the de Sitter solution for the next period. At the boundary, two mode functions have the same accuracy with error of O(Hi/k). We calculate the approximation up to the order of (Hi/k) 6 and show that the power spectrum of the scalar field fails to get corrections until we execute the approximation up to 6 th order.

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Section: Introductionmentioning

confidence: 91%

Revisiting the spectrum of a scalar field in an anisotropic universe

Kim

Minamitsuji

2014

Journal of the Korean Physical Society

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“…As shown in Ref. [17], the geometry is closely connected with the anti-de Sitter black brane solution discovered by Lemos [18]. The other solution, ds 2 := ds 2 s , has an initial singularity and their scale factors are given by…”

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confidence: 83%

Evolution of cosmological event horizons in anisotropic universes

Kim

2012

Journal of the Korean Physical Society

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We study the evolution of cosmological event horizons in anisotropic Kasner universes in the presence of a positive cosmological constant by analyzing null geodesics. At later times, the asymptotic form of cosmological horizons is the same spherical surface as the de Sitter horizon. At the early times, however, it has non-spherical shape with its eccentricity decreases with time. The horizon area increases with time respecting the second law of thermodynamics. The initial shape of the cosmological horizon takes the form of a needle or pancake surface depending on the nature of the background spacetimes. We also discuss that the presence of the holographic dark energy will modify significantly the initial evolution of the anisotropic universes.PACS numbers: 98.80. Bp,98.80.Jk Following the Copernican principle [1], the physical properties of the universe are spatially homogeneous viewed on a sufficiently large scale. This is consistent with nowadays experiments up to of order 10 −5 . Based on the principle, the Robertson-Walker spacetime with inflation at early stage, on which small perturbations evolve to give cosmological structures, is widely used to describe the present universe. However, there is no reason to believe that our universe was initially homogenous and isotropic. Generically, it could be highly inhomogeneous and anisotropic. The cosmic no-hair theorem [2] shows that in the presence of inflation most of the initially anisotropic cosmological spacetimes become isotropic rapidly if the matter fields residing in the universe satisfy the dominant energy condition. The theorem also implies that it is inevitable to have a highly anisotropic pre-inflationary universe if any small anisotropy remains after inflation. Since the anisotropy will be exponentially enhanced if we observe the universe backward in time and we cannot make that process stop by adding ordinary matters or radiations. The vestige of the pre-inflationary anisotropies can be seen through the large scale anomalies in the WMAP power spectra if the e-folding of inflation is not larger than 64 for GUT scale inflation. [3,4]. In fact, there is possibility that the effect of pre-inflationary anisotropies has been already detected in the Cosmic Microwave Background (CMB) temperature anisotropies, as an apparent alignment of the CMB multipoles on very large scales, so-called "Axis of Evil" [5-10] and giant rings [11].The standard cosmological model is the Λ-CDM model where most part of the universe is composed of the cosmological constant and cold dark matters. The spacetime has a future event horizon located at a distance R h = a(τ )where a(τ ) is the scale factor of the Robertson-Walker metric and τ is the comoving time. In the presence of asymptotically accelerating expansion of the universe, any observers will be surrounded by the future event horizon, which restricts the observers access to the information of the universe. This lack of information is represented by a kind of entropy proportional to the area of the cosmological horizon div...

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“…It, however, turns out that solutions with this more general ansatz are only either the pure AdS 4 or the BTZ black string 10 . For the case of non-warped solutions, e.g., H(z, ρ) = H(ρ), we obtain the most general static solutions with two-dimensional translation symmetry given by 10…”

Section: Hypercylindrical Solutionsmentioning

confidence: 98%

“…The geometrical properties of this class of solutions including their causal structures can be found in Ref. 10.…”

Section: Hypercylindrical Solutionsmentioning

confidence: 99%

Hypercylindrical Vacuum Spacetime Solutions

Kang

2012

Int. J. Mod. Phys. Conf. Ser.

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A brief report is given on hypercylindrical vacuum spacetime solutions and their geometrical properties. The five-dimensional Schwarzschild black string solution characterized by the mass density, which is known to reveal the so-called Gregory-Laflamme instability, turns out to be a special case of a wider class of hypercylindrical vacuum spacetime solutions characterized by two parameters, i.e., mass density and tension. Recent work on the solution space even including a momentum flow or a cosmological constant, higher dimensional extensions than five and some stability analysis under small perturbations are briefly summarized.

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String or branelike solutions in four-dimensional Einstein gravity in the presence of a cosmological constant

Cited by 4 publications

References 49 publications

Revisiting the spectrum of a scalar field in an anisotropic universe

Revisiting the spectrum of a scalar field in an anisotropic universe

Evolution of cosmological event horizons in anisotropic universes

Hypercylindrical Vacuum Spacetime Solutions

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