On the origin of the CDDR violation
  The investigation of any violation in the Cosmic Distance Duality Relation (CDDR) is one of the most important sources of investigation for a new physic. In this paper we propose a new method to find the origin of a possible violation on the CDDR. Such violation is defined from the equation $\frac{d_L}{d_A(1+z)^2} = \eta$, with $\eta \neq 1$. We analyze the observational constraints from SNIa, BAO and $f_{gas}$ for the parameter $\eta$ using three different parameterizations. We create three data sets with the following combinations: (Set I) $d_L$ data from SNIa and $d_A$ data from BAO measurements, (Set II) $d_L$ data from $f_{gas}$ and $d_A$ from BAO measurements and (Set III) $d_L$ from SNIa and $d_A$ from $f_{gas}$ measurements. The sets have 18 points and a redshift difference between the observational pairs of $\Delta z \leq 0.08$. It is found that the difference between Sets I and II is up to five times higher than Sets I and III, what suggest that a violation in the CDDR come from a new physics related with the angular diameter distance. 
R. S. Gon\c{c}alves
astro-ph.CO