CMB, as it leaves the surface of last scattering is linearly polarized. Generally, a linear polarization of an electro-magnetic wave could be expressed in terms of Stokes parameters Q and U. These quantities are NOT coordinate system independent. In order to create proper observables which are invariant with respect to a coordinate system, a new set of quantities are constructed using the Q and U Stokes parameters. These newly constructed variables are called the E and B-modes which are the most widely used description of polarization of the CMB.

My work primarily involves how intrinsic E and B modes of the CMB could change as it travels to us from the surface of last scattering. Galactic (and extra-galactic) magnetic field play a role in modifying the polarization of the CMB due to the intervening magnetic fields, which rotates the plane of polarization. This effect is known as the Faraday rotation and depends on frequency. Lower the frequency, the higher the rotation. This rotation effectively converts E modes into B modes, and as a result could potentially interfere with cosmological B-modes detection in the CMB expected due to primordial gravitational waves.

Recently, I have been involved with the circular polarization of the CMB. This is a rather unexplored territory with potentially a large reward. The CMB could be intrinsically circularly polarized due to Beyond Standard model or new physics effects. Circular polarization in the CMB could potentially point to new physics that are much harder to get to via high energy (and high cost) particle accelerators. However, the interfering foregrounds in this case are not very well known. One such potential foreground could be the galactic synchrotron emission which has a small degree of intrinsic circular polarization. I have developed a code to generate circular polarization maps due to the galactic synchrotron emission. This code uses Galactic magnetic field, relativistic electron densities to generate synchrotron emission along every line element (along the line of sight) using the HAMMURABI (which uses a HEALPIX pixelization scheme).

My most recent work on circular polarization of the CMB can be found here.

Magnetic field along the line of sight rotates the polarization of the electro-magnetic wave. This effect is known as the Faraday rotation. When a linearly polarized CMB passes through the galaxy, Faraday rotation affects the CMB polarization, causing generation of new B-modes, which are coordinate independent representation of linear polarization of an electro-magnetic wave. These B-modes are important to clean the data from lensing, determine galactic magnetic field from the CMB and also get a handle on the primordial magnetic field. See our paper at