What are recent observations telling us in light of improved tests of distance duality relation?

Liu Tonghua, Cao Shuo, Ma Shuai +3

As an exact result required by the Etherington reciprocity theorem, the cosmic distance duality relation (CDDR), $\eta (z)=D_L(z)(1+z{)}^{-2}/D_A(z)=1$ plays an essential part in modern…