# Are we living near the center of a local void?

## 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.

- Authors:

- Département de Physique Théorique and Center for Astroparticle Physics, Université de Genève, 24 quai Ansermet, CH-1211 Genève 4 (Switzerland)
- Institut d'Astrophysique de Paris, Université Pierre and Marie Curie—Paris V, CNRS-UMR 7095, 98 bis, Bd Arago, 75014 Paris (France)

- Publication Date:

- OSTI Identifier:
- 22679969

- Resource Type:
- Journal Article

- Resource Relation:
- Journal Name: Journal of Cosmology and Astroparticle Physics; Journal Volume: 2017; Journal Issue: 03; Other Information: Country of input: International Atomic Energy Agency (IAEA)

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ANGULAR CORRELATION; ANISOTROPY; CORRELATION FUNCTIONS; EMISSION; GRAVITATIONAL LENSES; POLARIZATION; RELICT RADIATION; SPHERICAL CONFIGURATION; SYMMETRY; VELOCITY

### Citation Formats

```
Cusin, Giulia, Pitrou, Cyril, and Uzan, Jean-Philippe, E-mail: giulia.cusin@unige.ch, E-mail: pitrou@iap.fr, E-mail: uzan@iap.fr.
```*Are we living near the center of a local void?*. United States: N. p., 2017.
Web. doi:10.1088/1475-7516/2017/03/038.

```
Cusin, Giulia, Pitrou, Cyril, & Uzan, Jean-Philippe, E-mail: giulia.cusin@unige.ch, E-mail: pitrou@iap.fr, E-mail: uzan@iap.fr.
```*Are we living near the center of a local void?*. United States. doi:10.1088/1475-7516/2017/03/038.

```
Cusin, Giulia, Pitrou, Cyril, and Uzan, Jean-Philippe, E-mail: giulia.cusin@unige.ch, E-mail: pitrou@iap.fr, E-mail: uzan@iap.fr. Wed .
"Are we living near the center of a local void?". United States.
doi:10.1088/1475-7516/2017/03/038.
```

```
@article{osti_22679969,
```

title = {Are we living near the center of a local void?},

author = {Cusin, Giulia and Pitrou, Cyril and Uzan, Jean-Philippe, E-mail: giulia.cusin@unige.ch, E-mail: pitrou@iap.fr, E-mail: uzan@iap.fr},

abstractNote = {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.},

doi = {10.1088/1475-7516/2017/03/038},

journal = {Journal of Cosmology and Astroparticle Physics},

number = 03,

volume = 2017,

place = {United States},

year = {Wed Mar 01 00:00:00 EST 2017},

month = {Wed Mar 01 00:00:00 EST 2017}

}