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arXiv · 1609.02061

Are we living near the center of a local void?

Giulia Cusin·Cyril Pitrou·Jean-Philippe Uzan
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Abstract

The properties of the cosmic microwave background (CMB) temperature and polarisation anisotropies measured by a static, off-centered observer located in a local spherically symmetric void, are described. In particular in this paper we compute, together with the standard 2- point angular correlation functions, the off-diagonal correlators, which are no more vanishing by symmetry. While the energy shift induced by the off-centered position of the observer can be suppressed by a proper choice of the observer velocity, a lensing-like effect on the CMB emission point remains. This latter effect is genuinely geometrical (e.g. non-degenerate with a boost) and reflects in the structure of the off-diagonal correlators. At lowest order in this effect, the temperature and polarisation correlation matrices have non-vanishing diagonal elements, as usual, and all the off-diagonal terms are excited. This particular signature of a local void model allows one, in principle, to disentangle geometrical effects from local kinematical ones in CMB observations.

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Giulia Cusin, Cyril Pitrou, Jean-Philippe Uzan. 2016-09-07. Are we living near the center of a local void?. https://doi.org/10.1088/1475-7516%2F2017%2F03%2F038

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