Cosmic Microwave Background Anisotropy from Nonlinear Structures in Accelerating Universes

Abstract

We study the cosmic microwave background (CMB) anisotropy due to spherically symmetric nonlinear structures in flat universes with dust and a cosmological constant. By modeling a time-evolving spherical compensated void/lump by Lemaitre-Tolman-Bondi spacetimes, we numerically solve the null geodesic equations with the Einstein equations. We find that a nonlinear void redshifts the CMB photons that pass through it regardless of the distance to it. In contrast, a nonlinear lump blueshifts (or redshifts) the CMB photons if it is located near (or sufficiently far from) us. The present analysis comprehensively covers previous works based on a thin-shell approximation and a linear/second order perturbation method and the effects of shell thickness and full nonlinearity. Our results indicate that, if quasi-linear and large ($>100$Mpc) voids/lumps would exist, they could be observed as cold or hot spots with temperature variance $>10^{-5}$K in the CMB sky.

7 pages, 4 figures, discussions on linear ISW effects added

References in corpus (2)

• Extragalactic Radio Sources and the WMAP Cold Spot
• Local Voids as the Origin of Large-angle Cosmic Microwave Background Anomalies: The Effect of a Cosmological Constant

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