What does the TE CMB spectrum reveal?

In summary, according to Will Kinney, the TE polarization spectrum measured by the Planck and WMAP satellites shows evidence for superhorizon fluctuations at low multipoles, which is consistent with pre-bigbang inflation. This is further supported by the negative peak in the TE cross-correlation power spectrum near ##\ell=100##. The presence of superhorizon perturbations is a powerful test for inflation, as it is a unique prediction that cannot be produced by any purely causal theory in an expanding universe.
  • #1
Rene Kail
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Does the polarization spectrum TE measured by the Planck and WMAP satellites show evidence for superhorizon fluctuations at low multipoles and are these evidence for pre-bigbang inflation?
 
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  • #2
Rene Kail said:
Does the polarization spectrum TE measured by the Planck and WMAP satellites show evidence for superhorizon fluctuations at low multipoles and are these evidence for pre-bigbang inflation?
According to Will Kinney, yes. Kinney is a professor of Physics at SUNY Buffalo.

In chapter 6 of his recent book (see below) he presents a figure of the TE cross-correlation power spectrum showing an anti-correlation at low multipole moments assigned as superhorizon modes. Unfortunately, no reference to the literature is given.

The actual power spectrum is from the Planck collaboration. I checked that, although I fail to recall from which of their many papers.

Will Kinney, An Infinity of Worlds: Cosmic Inflation and the Beginning of the Universe, The MIT Press, 2022.
 
  • #3
To elaborate the comments made in Post #2. The TE cross-correlation power spectrum (courtesy of NASA/LAMBDA Archive Team) from the Planck mission is illustrated below:
te_spectrum_2020aug_1024.png


It is the negative going peak in the power spectrum near ##\ell=100## that Kinney attributes to evidence consistent with superhorizon modes and thus with inflation.

Kinney said:
By far the most powerful general test of inflation is the presence of superhorizon perturbations. This is a prediction that is, at least in the case of an expanding universe, unique to inflation ... , and does not depend on any particular model for inflation. No purely causal theory in an expanding universe can produce superhorizon perturbations.
 

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