Spectro-spatial evolution of the CMB I: discretisation of the thermalisation Green's function

Understand

Spectral distortions of the cosmic microwave background (CMB) have been recognized as an important future probe of the early Universe.

• Existing theoretical studies primarily focused on describing the evolution and creation of average distortions, ignoring spatial perturbations in the plasma.
• One of the main reasons for this choice is that a treatment of the spectro-spatial evolution of the photon field deep into the primordial Universe requires solving a radiative transfer problem for the distortion signals, which in full detail is computationally challenging.
• Here we provide the first crucial step towards tackling this problem by formulating a new spectral discretisation of the underlying average thermalisation Green's function.