Low-ℓ CMB from string-scale SUSY breaking?
Modern Physics Letters A
Models of inflation are instructive playgrounds for supersymmetry breaking in Supergravity and String Theory. In particular, combinations of branes and orientifolds that are not mutually BPS can lead to brane supersymmetry breaking, a phenomenon where non--linear realizations are accompanied, in tachyon--free vacua, by the emergence of steep exponential potentials. When combined with milder terms, these exponentials can lead to slow--roll after a fast ascent and a turning point. This leaves
... nd distinctive patterns of scalar perturbations, where pre--inflationary peaks can lie well apart from an almost scale invariant profile. I review recent attempts to connect these power spectra to the low--ℓ CMB, and a corresponding one--parameter extension of ΛCDM with a low--frequency cut Δ. A detailed likelihood analysis led to Δ = (0.351 ± 0.114) × 10^-3 Mpc^-1, at 99.4% confidence level, in an extended Galactic mask with f_sky=39%, to be compared with a nearby value at 88.5% in the standard Planck 2015 mask with f_sky=94%. In these scenarios one would be confronted, in the CMB, with relics of an epoch of deceleration that preceded the onset of slow--roll.