B-mode delensing for the Simons Observatory

University of Cambridge & Simons Observatory Collaboration, supervised by Anthony Challinor and Blake Sherwin

The Simons Observatory (SO) will target B-mode polarization anisotropies in the CMB to infer the tensor-to-scalar ratio (amplitude of inflationary gravitational waves). This faint signal must be disentangled from much brighter emissions by our own Galaxy, and from secondary B-modes produced by weak gravitational lensing. During my PhD, I worked on a pipeline performing both foregroung cleaning and delensing simultaneously, aiming to go from sky maps to unbiased and precise constraints on inflationary physics. The methods and results are presented in detail in this paper.

  • The following code estimates the lensing deflection field from a combination of CMB maps and external data, and builds a template of the lensing B-modes.

Lensing reconstruction code

  • The main analysis pipeline then takes observed sky maps and the lensing template as inputs, and outputs posterior distributions for our model parameters. We use maps in 6 frequency channels to constrain and clean Galactic foregrounds.

Component separation code

  • Demonstration on simulated maps: the template accurately captures the true lensing B-modes, and including it in the analysis leads constraints on the tensor-to-scalar ratio to visibly tighten.

Results on simulations

Lattice simulations of false vacuum decay

University of Cambridge & QSimFP Consortium, in collaboration with Hiranya Peiris and Alex Jenkins

Model-independent anomaly detection in gravitational waves

EPFL LPPC, supervised by Sergey Sibiryakov and Inar Timiryasov

Time-delay cosmography with strongly lensed quasars

EPFL LASTRO, supervised by Frederic Courbin and Aymeric Galan

TDLMC pipeline found here https://github.com/TDCOSMO/hierarchy_analysis_2020_public/tree/master/TDLMC

CHIME radiotelescope calibration

UBC Vancouver, supervised by Gary Hinshaw and Mateus Fandino