Donough Regan

CMB lensing and primordial squeezed non-gaussianity

Squeezed primordial non-Gaussianity can strongly constrain early-universe physics, but it can only be observed on the CMB after it has been gravitationally lensed. We give a new simple non-perturbative prescription for accurately calculating the effect of lensing on any squeezed primordial bispectrum shape, and test it with simulations. We give the generalization to polarization bispectra, and discuss the effect of lensing on the trispectrum. We explain why neglecting the lensing smoothing effect does not significantly bias estimators of local primordial non-Gaussianity, even though the change in shape can be >~10%. We also show how tau_NL trispectrum estimators can be well approximated by much simpler CMB temperature modulation estimators, and hence that there is potentially a ~10-30% bias due to very large-scale lensing modes, depending on the range of modulation scales included. Including dipole sky modulations can halve the tau_NL error bar if kinematic effects can be subtracted using known properties of the CMB temperature dipole. Lensing effects on the g_NL trispectrum are small compared to the error bar. In appendices we give the general result for lensing of any primordial bispectrum, and show how any full-sky squeezed bispectrum can be decomposed into orthogonal modes of distinct angular dependence.

Planck Trispectrum Constraints on Primordial Non-Gaussianity at Cubic Order

Non-Gaussianity of the primordial density perturbations provides an important measure to constrain models of inflation. At cubic order the non-Gaussianity is captured by two parameters

Towards optimal cosmological parameter recovery from compressed bispectrum statistics

\tau_{\rm NL}

Influence of large local and non-local bispectra on primordial black hole abundance

and

Constraining Galileon inflation

g_{\rm NL}

The bispectrum of cosmic string temperature fluctuations including recombination effects

that determine the amplitude of the density perturbation trispectrum. Here we report measurements of the kurtosis power spectra of the cosmic microwave background (CMB) temperature as mapped by Planck by making use of correlations between square temperature-square temperature and cubic temperature-temperature anisotropies. In combination with noise simulations, we find the best joint estimates to be

Principal components of CMB non-Gaussianity

\tau_{\rm{NL}}=0.3 \pm 0.9 \times 10^4

The bispectrum of matter perturbations from cosmic strings

and

Consistency relations in effective field theory

g_{\rm{NL}}=-1.2 \pm 2.8 \times 10^5

An inventory of bispectrum estimators for redshift space distortions

. If