<i>Euclid</i>: Forecast constraints on the cosmic distance duality relation with complementary external probes
<i>Euclid</i>: Forecast constraints on the cosmic distance duality relation with complementary external probes
In metric theories of gravity with photon number conservation, the luminosity and angular diameter distances are related via the Etherington relation, also known as the distance-duality relation (DDR). A violation of this relation would rule out the standard cosmological paradigm and point at the presence of new physics. We quantify …