1/f noise and CMB map making: new semi-analytic results on polarization modulation
I will discuss the impact of 1/f noise, also known as low frequency excess noise, in measuring the large angle CMB temperature and polarization anisotropies. CMB and many other measurements cannot be absolute because the detector zero-point undergoes low-frequency fluctuations whose expectation value is formally divergent. Only differences in measurements closely spaced in time are physically meaningful and exploitable. I discuss how this difficulty has been dealt with over the years starting with the work of Dicke in 1947 and going to modern optimal map making techniques made possible by modern supercomputing. I will also present some new analytic results on predicting the impact of 1/f noise on the final maps that do not rely on supercomputer simulations. Implications for future B mode experiments will be discussed. 1/f noise occurs in a wide range of physical contexts and I will briefly discuss the mixed success of attempts seeking a universal explanation for the origin of 1/f noise.