Nordita HEP Local Seminars

Non-Gaussianity and New Probes of Spatial Curvature

by Sadra Jazayeri (Cambridge U., DAMTP)

Europe/Stockholm
132:028

132:028

Description
Cosmological observations have virtually saturated their maximum precision in determining the value of the spatial curvatures, and by far CMB and BAO data are consistent with a flat background geometry. Given that direct measurements of Ωk will be unlikely to improve the current bounds in any foreseeable future, it is important to look out for indirect signals sensitive to a non-vanishing Ωk. In this work, we inspect the interplay between non-gaussianity and the spatial curvature. We point out that in the presence of equilateral and orthogonal non-gaussianities, the consistency demands a new signal to exist already in the power spectrum. We study how this new signal can lead to improved constraints on Ωk and non-gaussianity by looking at the measured low-ell` values of CMB TT multipoles, and we discuss the subtleties present in the perturbative treatment of Ωk. In addition, we compute the modification of the bispectrum up to leading order in Ωk, and we present the observational bounds on the size of the signal in the squeezed and equilateral shapes of the three-point function. In passing, we study adiabatic modes in curved universes. We find that there are no adiabatic modes and therefore soft theorems, such as the consistency relation of Maldacena, are generally violated.