Inhomogeneity and the foundations of concordance cosmology

The apparent accelerating expansion of the Universe is forcing us to examine the foundational aspects of the standard model of cosmology -- in particular, the fact that dark energy is a direct consequence of the homogeneity assumption. We discuss the foundations of the assumption of spatial homogeneity, in the case when the Copernican Principle is adopted. We present results that show how (almost-) homogeneity follows from (almost-) isotropy of various observables. The analysis requires the fully nonlinear field equations -- i.e., it is not possible to use second- or higher-order perturbation theory, since one cannot assume a homogeneous and isotropic background. Then we consider what happens if the Copernican Principle is abandoned in our Hubble volume. The simplest models are inhomogeneous but spherically symmetric universes which do not require dark energy to fit the distance modulus. Key problems in these models are to compute the CMB anisotropies and the features of large-scale structure. We review how to construct perturbation theory on a non-homogeneous cosmological background, and discuss the complexities that arise in using this to determine the growth of large-scale structure.Comment: 26 pages and 1 figure. Invited review article for the CQG special issue on nonlinear cosmological perturbations. v2 has additional refs and comments, minor errors corrected, version in CQ

Tenuous Types - Scraper Reduction Continuums in the Eastern Victoria River Region, Northern Territory

To better understand the relationship between changing retouched implement morphology and intensity of reduction, archaeologists must develop measures of morphological change that work outside of, and challenge, existing typologies. This paper attempts such an approach by exploring changes in four aspects of implement morphology as retouch increases, using a population of scrapers - or non-formally retouched flakes - from four rockshelters in northern Australia. The results allow the formulation of a reduction model that accounts for many of the differences in implement morphology that underlie most traditional scraper typologies. The results provide the basis for a critique of an early but influential scraper typology that underlies most Australian classifications in use today