Planck's summer: gauge independence of cosmological surveys
17 Jul 2013third post in the “Planck’s summer”-series by Youness: Power spectra in linear perturbation theory depend on the gauge chosen. The differences are small on scales well within the horizon, but they grow as we go to very large scales. However, observers apparently measure galaxy positions unambiguously and calculate power spectra from this. How would you interpret their data on the largest scales?