Can the Distance?Redshift Relation be Determined from Correlations between Luminosities?

We explore whether an independent determination of the distance-redshift relation, and hence cosmological model parameters, can be obtained from apparent correlations between two different waveband luminosities or fluxes, as has been claimed in recent works using X-ray ultraviolet fluxes quasars. show that such is possible only if correlation model, measured redshifts; for example, being based on sound theoretical models unrelated observations. In particular, we determined empirically redshifts, then method suffers circularity. case, works, observed very narrow redshift bins are used proxy luminosity correlation, one dealing with a pure tautology no information distances model. argue problem arises because incomplete treatment use numerical methods joint quasar data set to demonstrate this shortcoming.