Searcharxiv⌕ Search
Home/Archive/arXiv

arXiv · gr-qc/9804018

Multidimensional perfect fluid cosmology with stable compactified internal dimensions

U. Guenther·A. Zhuk
View original source ↗Read source document ↗Export metadata ↓

Abstract

Multidimensional cosmological models in the presence of a bare cosmological constant and a perfect fluid are investigated under dimensional reduction to 4-dimensional effective models. Stable compactification of the internal spaces is achieved for a special class of perfect fluids. The external space behaves in accordance with the standard Friedmann model. Necessary restrictions on the parameters of the models are found to ensure dynamical behavior of the external (our) universe in agreement with observations.

Explore related subjects

gr-qcastro-phhep-th

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

U. Guenther, A. Zhuk. 1998-04-06. Multidimensional perfect fluid cosmology with stable compactified internal dimensions. https://doi.org/10.1088/0264-9381%2F15%2F7%2F017

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Massive Scalar Quasinormal Modes and Quasibound States of Charged Black Holes with Logarithmic corrections

We study how long-range deformations in a black-hole metric affect the oscillation, trapping, and decay of a neutral, minimally coupled massive scalar field. We choose a logarithmic deformation of Reissner-Nordström (RN) sourced by nonlinear electrodynamics. It provides an exact solution of Einstein gravity and admits a finite completion. The same geometry also arises in a phenomenological perfect-fluid dark-matter model. In this setup, we analyze both quasinormal modes (QNMs), which describe relaxation, and quasibound states (QBSs), which describe trapped modes with small horizon absorption. We first show that a small scalar mass moves the potential barrier outward, raises it, and reduces its curvature. First-order WKB then predicts weaker damping at every fixed finite multipole and overtone. We then compare several approaches, namely sixth-order WKB, global matching, a generalized Leaver method (adapted to the logarithmic geometry) and time-domain evolution. All methods yield consistent QNM estimates within their ranges of validity. Global matching and Leaver also agree closely for QBSs. Further analytic estimates with a reference trapped state show that a local Padé approximation gives a binding-energy error of about $0.04\%$, while leading Gamow tunnelling underestimates damping by about $25\%$. Across the sampled QBSs, increasing the scalar mass or nonlinear coupling strengthens binding but shortens the lifetime through greater horizon absorption. Finally, using an appropriate horizon regularization and a common complex radial contour, we demonstrate orthogonality of an independently computed QNM-QBS pair using a suitable relativistic bilinear framework.

gr-qc↗
arXiv2026

HWF Analysis of TRN Black Holes

We extend the horizon wave-function (HWF) formalism to a spherically symmetric, charged, spinless quantum source in $\mathcal{D} + 1$ dimensional spacetime geometry and construct the HWFs associated with inner- as well as outer-horizons of the Tangherlini--Reissner--Nordström (TRN) black hole. The corresponding black hole formation probabilities, $P_{\rm BH}^{\pm}$, are also calculated and their sensitivities due to various source parameters including charge, mass, and $\mathcal{D}$ are analysed as well. Our analysis reveals that the ratio of inner- to outer-horizon probabilities, $P_{\rm BH}^{-}/P_{\rm BH}^{+}$, changes drastically from being unity as the source departs away from being in the extremal limit defined by $α$ ($\to 1$ for extremal case). Furthermore, black hole formation probabilities are found to be highly suppressed for higher values of $\mathcal{D}$, particularly for the source mass, $m \lesssim Λ_{\mathcal{D}}$, e.g., for $α= 0.5$, the ratio, $P_{\rm BH}^{+}(\mathcal{D} = 5)/P_{\rm BH}^{+}(\mathcal{D}=10)$ turn out to be approximately $2.95\times10^3$, $117$, and $3.35$ respectively for $m/Λ_{\mathcal{D}} = 0.5, 1$ and $2$, with $Λ_{\mathcal{D}}$ being the reduced gravity scale associated with $\mathcal{D}$ spatial-dimensions.

gr-qc↗
arXiv2026

More Eccentric, Not Always Less Detectable: High Mass Holds Its Ground, Low Mass Loses Reach

Gravitational waves from eccentric compact binary coalescences trace dynamical binary formation, but matched-filtering searches responsible for most detections rely on quasicircular templates. Quantifying any sensitivity loss is crucial for assessing population completeness and the need for dedicated eccentric template banks. We present the first systematic GstLAL search study spanning eccentricities up to $e_{\rm 15Hz}=0.99$ and broad ranges of chirp mass, mass ratio, inclination, and aligned spin. Using TEOBResumS-Dalí waveforms, we inject eccentric signals and measure recovered signal-to-noise ratio, signal-consistency statistics, false-alarm rate, and sensitive volume and distance. For high-mass binaries ($\mathcal{M}_c\gtrsim30\,M_\odot$), sensitive distance is nearly independent of eccentricity, demonstrating that greater eccentricity does not necessarily reduce search sensitivity. In contrast, for low-mass binaries, sensitive distance falls by up to $\sim50\%$ near $e_{\rm 15Hz}\approx0.75$. Although the absolute loss in reach is modest given their low quasicircular sensitivity, this relative reduction exceeds the increase in sensitive distance between the second and third observing runs of the LIGO--Virgo--KAGRA collaboration and is consistent with previous low-mass studies. We also find that waveform matches at fixed source parameters substantially overpredict search sensitivity loss, meaning that the pipeline's signal-consistency test and maximization over its template bank mitigate much of the predicted sensitivity loss. This highlights the need for end-to-end injection campaigns to establish the detectability of eccentric binaries.

gr-qc↗