Age Problem in Lemaitre-Tolman-Bondi Void Models

TL;DR

This paper evaluates LTB void models as an alternative to dark energy for cosmic acceleration, testing their compatibility with old high redshift objects and highlighting tensions with other observational constraints.

Contribution

It provides a detailed analysis of LTB void models using high redshift objects, revealing significant tensions in model parameters with other cosmological data.

Findings

Large void sizes are needed to fit old high redshift objects.

Tensions exist between void size parameters from different observations.

Lower age limits for quasars can reduce model tensions.

Abstract

As is well known, one can explain the current cosmic acceleration by considering an inhomogeneous and/or anisotropic universe (which violates the cosmological principle), without invoking dark energy or modified gravity. The well-known one of this kind of models is the so-called Lema\^{\i}tre-Tolman-Bondi (LTB) void model, in which the universe is spherically symmetric and radially inhomogeneous, and we are living in a locally underdense void centered nearby our location. In the present work, we test various LTB void models with some old high redshift objects (OHROs). Obviously, the universe cannot be younger than its constituents. We find that an unusually large $r_0$ (characterizing the size of the void) is required to accommodate these OHROs in LTB void models. There is a serious tension between this unusually large $r_0$ and the much smaller $r_0$ inferred from other observations (e.g. SNIa, CMB and so on). However, if we instead consider the lowest limit 1.7\,Gyr for the quasar APM 08279+5255 at redshift $z=3.91$, this tension could be greatly alleviated.