* Astronomy

Title: Using quasars as standard clocks for measuring cosmological redshift
Authors: De-Chang Dai, Glenn D. Starkman, Branislav Stojkovic, Dejan Stojkovic, Amanda Weltman

We report hitherto unnoticed patterns in quasar light curves. We characterise segments of quasars' light curves with the slopes of the straight lines fit through them. These slopes appear to be directly related to the quasars' redshifts. Alternatively, using only global shifts in time and flux, we are able to find significant overlaps between the light curves of different pairs of quasars by fitting the ratio of their redshifts. We are then able to reliably determine the redshift of one quasar from another. This implies that one can use quasars as standard clocks, as we explicitly demonstrate by constructing two independent methods of finding the redshift of a quasar from its light curve.

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The sample of quasars with different redshifts. Time is transformed to the quasar rest frame (i.e. divided by (z +1)). A pattern emerges, some parallel lines (same slopes) appear. We mark them with the thin black lines. A possible shallower, long-term trend is indicated by thick green lines.