Photons can be blueshifted after being scattered by excited free electrons in galaxy clusters (Sunyaev-Zeldovich effect).
The kinetic version of this effect occrus because electrons are accelerated. I've read that the kinetic SZ signal is sensitive to both the expansion history and the dynamics of cosmological perturbations... But I don't understand this completely...
Therefore, does the expansion of the universe affect this in some way?
