Probing violation of the Copernican principle via the integrated Sachs-Wolfe effect

Kenji Tomita and Kaiki Taro Inoue
Phys. Rev. D 79, 103505 – Published 7 May 2009

Abstract

Recent observational data of supernovae point to Λ-dominated flat cosmological models. However, an alternative model in which we happen to live in an underdense region requires no dark energy or modification of gravity. This challenges the Copernican principle. We show that the integrated Sachs-Wolfe (ISW) effect is an excellent discriminator between anti-Copernican inhomogeneous models and the standard Copernican models. As a reference model, we consider an anti-Copernican inhomogeneous model that consists of two inner negatively curved underdense regions and an outer flat Einstein-de Sitter region. We assume that these regions are connected by two thin walls at redshifts z=0.067 and z=0.45. In the inner two regions, the first-order ISW effect is dominant and comparable to that in the concordant flat-Λ models. In the outer Einstein-de Sitter region, the first-order ISW effect vanishes but the second-order ISW effect plays a dominant role, while the first-order ISW effect is dominant in the flat-Λ models at moderate redshifts. This difference can discriminate the anti-Copernican models from the concordant flat-Λ model. At high redshifts, the second-order ISW effect is dominant both in our inhomogeneous model and in the concordant model. In the outer region, moreover, the ISW effect due to large-scale density perturbations with a present matter density contrast ϵm00.37 is negligible, while the effect due to small-scale density perturbations (such as clusters of galaxies, superclusters, and voids) with ϵm00.37 would generate anisotropies which are larger than those generated by the ISW effect in the concordant model.

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  • Received 9 March 2009

DOI:https://doi.org/10.1103/PhysRevD.79.103505

©2009 American Physical Society

Authors & Affiliations

Kenji Tomita

  • Yukawa Institute for Theoretical Physics, Kyoto University, Kyoto 606-8502, Japan

Kaiki Taro Inoue

  • Department of Science and Engineering, Kinki University, Higashi-Osaka, 577-8502, Japan

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Issue

Vol. 79, Iss. 10 — 15 May 2009

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