Long gradient mode and large-scale structure observables

Alireza Allahyari (Sharif University of Technology)
Tuesday, 94/09/03 (November 24, 2015), 13:30

Abstract
We extend the investigation of the long mode effects to other large scale observables most importantly galaxy number counts and their observed power spectrum. When defined correctly, genuine observables should not only be gauge invariant but also devoid of any gauge artifacts. One such gauge artifact is a pure gradient mode. We confirm that a long gradient mode which is still outside observer's horizon leaves no imprint on the large scale observables at first order dealing with the complexities that arise from the bias relation in the first formulation. It is especially shown that the general relativistic bias relation for the halos and galaxies is invariant under the presence of a long gradient mode perturbation. We also confirm that the galaxy number counts are not affected by these modes. The observed power spectrum also remains unaffected.