Search arXiv⌕ Search
Home/Archive/arXiv

arXiv · gr-qc/0702043

On the onset of cosmological backreaction

Nan Li·Dominik J. Schwarz
View original source ↗Read source document ↗Export metadata ↓

Abstract

Cosmological backreaction has been suggested as an explanation of dark energy and is heavily disputed since. We combine cosmological perturbation theory with Buchert's non-perturbative framework, calculate the relevant averaged observables up to second order in the comoving synchronous gauge, and discuss their gauge dependence. With the help of an integrability condition the leading second order contributions follow from the first order calculation. We focus on the onset of cosmological backreaction, as a perturbative treatment is necessarily restricted to the era when the effect is still small. We demonstrate that the leading contributions to all averaged physical observables are completely specified on the boundary of the averaged domain. For any finite domain these surface terms are nonzero in general and thus backreaction is for real. We map the backreaction effect on an effectively homogeneous and isotropic fluid. The generic effective equation of state is not only time dependent, but also depends on scale.

Explore related subjects

gr-qcastro-phhep-phhep-th

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Nan Li, Dominik J. Schwarz. 2007-09-17. On the onset of cosmological backreaction. https://doi.org/10.1103/physrevd.76.083011

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↗