Search arXiv⌕ Search
Home/Archive/arXiv

arXiv · gr-qc/0109039

Anisotropic cosmologies containing isotropic background radiation

Saulo Carneiro·Guillermo A. Mena Marugan
View original source ↗Read source document ↗Export metadata ↓

Abstract

We present an anisotropic cosmological model based on a new exact solution of Einstein equations. The matter content consists of an anisotropic scalar field minimally coupled to gravity and of two isotropic perfect fluids that represent dust matter and radiation. The spacetime is described by a spatially homogeneous, Bianchi type III metric with a conformal expansion. The model respects the evolution of the scale factor predicted by standard cosmology, as well as the isotropy of the cosmic microwave background. Remarkably, the introduction of the scalar field, apart from explaining the spacetime anisotropy, gives rise to an energy density that is close to the critical density. As a consequence, the model is quasiflat during the entire history of the universe. Using these results, we are also able to construct approximate solutions for shear-free cosmological models with rotation. We finally carry out a quantitative discussion of the validity of such solutions, showing that our approximations are acceptably good if the angular velocity of the universe is within the observational bounds derived from rotation of galaxies.

Explore related subjects

gr-qcastro-ph

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Saulo Carneiro, Guillermo A. Mena Marugan. 2001-09-11. Anisotropic cosmologies containing isotropic background radiation. https://doi.org/10.1103/physrevd.64.083502

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

KEEP EXPLORING

Related papers

arXiv2026

An upper bound on the minimum orbital period of black holes

Previous research has focused on establishing lower bounds on the minimum orbital period of black holes. In this work, we explore the complementary question of whether an upper bound exists for the minimum orbital period of black holes. We investigate the minimum orbital periods of three types of black holes: Schwarzschild, Reissner-Nordström and Kerr-Newman black holes. We find that the minimum orbital period of these black holes is bounded by an upper limit $T_{min} \leqslant 6\sqrt{3}πM$, where $M$ is the black hole mass. Our results suggest that this upper bound on the minimum orbital period may be a general property in black hole spacetimes.

gr-qc↗
arXiv2026

Bounds on the minimum orbital period in the background of 5-dimensional charged black holes

In this paper, we study the upper and lower bounds on the minimum orbital period of 5-dimensional charged black holes. Our results indicate that the upper bound of the minimum orbital period corresponds to non-charged black holes, while the lower bound is achieved in the case of maximally charged black holes. We further establish precise analytical expressions for the upper and lower bounds of the minimum orbital period. Our findings provide valuable insights into 5-dimensional charged black holes and help constrain theoretical gravity models.

gr-qc↗
arXiv2026

Analysis of minimum orbital periods around d-dimensional charged black holes

This paper investigates the bounds on the minimum orbital period for test objects around d-dimensional charged black holes in asymptotically flat spacetimes. We derive the exact critical radius and the minimum orbital period. We then prove analytically that the minimum orbital period decreases strictly as the charge of the black hole increases. Thus, the upper limit is reached for an uncharged black hole, while the lower limit is attained for a maximally charged one, and the two bounds take the closed form $\frac{2π(d-2)}{d-3}[(d-2)M]^{\frac{1}{d-3}}\leqslant T_{min} \leqslant 2π\sqrt{\frac{d-1}{d-3}}\,[(d-1)M]^{\frac{1}{d-3}}$. Since the minimum period equals $2π$ times the shadow radius, the upper bound is equivalently a universal upper bound on the shadow radius. These results improve our understanding of dynamics around d-dimensional black holes and impose constraints on candidate gravity theories.

gr-qc↗