Weak gravitational lensing & CMB probes of spatially varying fine-structure constant and baryon/dark-matter relative abundances.
Abstract
Cosmic microwave background (CMB) anisotropies are Gaussian and isotropic at linear order. The presence of long wavelength modulating fields, however, can introduce non-Gaussianity and statistical anisotropy in the CMB. For example, the dark matter present along the line of sight between observers and the last-scattering surface gravitationally lenses the background CMB. Weak gravitational lensing of the CMB has already been detected at ~40 \sigma in Planck satellite data! There are discrepancies between the observed CMB lensing signal and expectations from $\Lambda$CDM theory, offering the opportunity to explore the possibility of other long wavelength modulating field, which might be able to relieve the tension between the predicted and observed amplitude of CMB weak lensing. A variety of particle-physics models for the origin of the baryon asymmetry and density fluctuations in the universe predict compensated isocurvature perturbations, spatial fluctuations in the relative densities of baryons and cold dark matter. It is also possible that the strength of the electromagnetic interaction is set by a novel scalar field with couplings to the standard model, sourcing spatial fluctuations in the fine structure constant. Here, the observational motivation for these models is reviewed and the imprint of both these possibilities on CMB statistics (and weak lensing observables in particular) is computed. Current data are used to probe these models, forecasts are made for the sensitivity of upcoming efforts like CMB Stage IV and the Simons Array, and a variety of other theoretical considerations are explored.
- Publication:
-
American Astronomical Society Meeting Abstracts #233
- Pub Date:
- January 2019
- Bibcode:
- 2019AAS...23314203G