Date:
Thursday, April 4, 2024, 11:00am to 12:00pm
Paul Shellard (University of Cambridge)
"The Bispectrum as a Probe of the Primordial Universe and Late-time Nonlinear Clustering"
The three-point correlator or bispectrum is a key observable for both CMB maps and galaxy surveys, which also opens a window on the early universe. While nearly scale-invariant Gaussian initial conditions are in excellent agreement with observation, all theories exhibit some deviation from Gaussianity due to nonlinear interactions, which the bispectrum may reveal. The MODAL bispectrum estimator, exploiting separable eigenmodes, continues to be extended to constrain the widest array of inflationary models using the Planck CMB data (soon to be improved with SO maps), whether DBI inflation, oscillatory models or the cosmological correlator. Linked to the efficient PriMODAL code calculating high-precision QFT bispectra, the bispectrum becomes a quantitative probe of fundamental theory. Forecasts suggest that galaxy surveys will offer the largest sensitivity improvements, so the MODAL_LSS pipeline has been adapted to estimate both full 3D and projected 2D bispectra. In this case, the signal due to late-time nonlinear clustering must be disentangled, for which the effective field theory approach (EFTofLSS) provides a reliable framework.
See also: 2023-24