UMICH-2015: Response to Inflation Action Items

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Action Items: updated list, with names (November 2, 2015)

Start writing (making a strong case for r)

RF and SS will get started right away.

Prospects for r and nt for various configurations and values of r

(Fisher matrix forecasts including foregrounds that will feed into more detailed simulations)


Possibility to establish departure from scale invariance even for extended parameters space for both S3 and S4


Improvements on other inflationary observables (running, non-Gaussianity, etc. while varying neutrino mass/Neff)


Inflationary Models that CMB S4 could see hints for (e.g. modulated reheating)

Joel Meyers

Dependence of error bars on lmin

Several observables display a dependence on lmin that motivates lmin=14. One example is the optical depth.


It is shown as a function of lmin for two values of the optical depth and two reionization histories. Parameters degenerate with it inherit the strong dependence. The reionization histories corresponding to the various curves are shown in the next plot. This is largely independent of the reionization history.


The multipole range that contains most of the information does not significantly depend on the reionization history but does depend on the optical depth. The effect of the different reionization histories on the angular power spectra is shown in the next plot.

Clee dzr.png

Science drivers that would affect design of experiment

Light axions with masses between 10^-33 eV and 4x10^-28 eV (not the QCD axion) would lead to an isotropic rotation by ~9 arcmin (independent of the axion decay constant). This would be rotated away by EB nulling. (The mass range is such that they oscillate between recombination and today, but not long before recombination).

The absolute polarization angles are currently typically calibrated to around 1 degree. To detect such axions or rule them out, one would have to calibrate the polarization angles at ~3 arcmin.

A very neat idea to achieve this goal was recently proposed in

Isocurvature forecasts

How should we parameterize?

Julien Lesgourgues

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