Real space tomography of the primordial Universe with cluster polarization

We describe how a survey of the polarization of the cosmic microwave background induced by Compton scattering in galaxy clusters can be used to make a full spatial reconstruction of the primordial (z∼1089) matter distribution inside our surface of last scattering. This “polarization tomography” can yield a spatial map of the initial state of the Universe just as gravitational collapse was beginning to drive structure formation. We present a transparent method and simple formulas from which one can compute the 3D primordial map in real and in Fourier space, given a 3D map of the polarization due to galaxy clusters. The advantage of the real space reconstruction is that it is free from the statistical uncertainties which are inherent in the Fourier space reconstruction. We discuss how noise, partial sky covering and depth of the survey can affect the results.