Speaker
Description
In this talk, we present a novel framework to compute gauge-invariant cosmological observables, such as the luminosity distance–redshift relation, the redshift drift, and the relation between galaxy number counts and luminosity distance. Our approach is based on constructing first- and second-order perturbations around a homogeneous and isotropic background within geodesic light-cone (GLC) coordinates. By exploiting the gauge freedom of light-cone perturbations, we fix the GLC gauge and obtain a particularly convenient description of observables defined on the observer’s past light cone.
In these coordinates, relativistic corrections to cosmological observables naturally arise as perturbations of the past light cone itself. A key advantage of the GLC gauge is that both time-like and null geodesics can be solved exactly for a generic space-time geometry. As a consequence, the Jacobi map can also be obtained in full generality, allowing for fully non-linear expressions for a wide range of cosmological observables.
Within this framework, we present a simplified method to derive non-linear, gauge-invariant relativistic corrections to cosmological observables, providing a powerful tool for the interpretation of precision cosmological measurements.