The Cold Spot as a Large Void: Lensing Effect on CMB Two and Three Point Correlation Functions

Understand

The "Cold Spot" in the CMB sky could be due to the presence of an anomalous huge spherical underdense region - a "Void" - of a few hundreds Mpc/h radius.

• Such a structure would have an impact on the CMB two-point (power spectrum) and three-point (bispectrum) correlation functions not only at low-l, but also at high-l through Lensing, which is a unique signature of a Void.
• Modeling such an underdensity with an LTB metric, we show that for the power spectrum the effect should be visible already in the WMAP data only if the Void radius is at least L \gtrsim 1 Gpc/h, while it will be visible by the Planck satellite if L \gtrsim 500 Mpc/h.
• We also speculate that this could be linked to the high-l detection of an hemispherical power asymmetry in the sky.