Astronomy and Astrophysics Seminars

Testing Cosmic Statistical Isotropy

by Prof. Tarun Souradeep (IUCAA, Pune)

Tuesday, January 16, 2018 from to (Asia/Kolkata)
at Lecture Theatre ( AG66 )
The standard model of cosmology predicts a statistically isotropic distribution of fluctuations in the measured Cosmic 
Microwave Background (CMB)  temperature and polarisation maps.  Enigmatic anomalies  claimed in the WMAP and 
Planck  CMB sky maps could  challenge the standard model. However, these claims need to be cast in an objective  
mathematical  framework  and established with statistical rigour.  We present a general method for Bayesian inference 
of the underlying covariance structure of random fields on a sphere. We employ the Bipolar Spherical Harmonic (BipoSH) 
representation of general covariance structure on the sphere. We illustrate the efficacy of the method with a principled 
approach to  assess violation of statistical isotropy (SI) in the sky maps of CMB fluctuations. We pay particular attention 
to quantifying the significance of the tentative evidence for a Cosmic Hemispherical asymmetry.