On time dilation in quasar light curves

TL;DR

This study investigates whether time dilation effects are observable in quasar light curves by comparing high and low redshift samples, finding no evidence of such effects, which challenges existing expectations.

Contribution

The paper provides the first direct measurement attempt of time dilation in quasar light curves using Fourier analysis across multiple timescales.

Findings

Quasar light curves do not exhibit expected time dilation effects.

Possible explanations include black hole growth offsetting time dilation or microlensing effects.

Results suggest re-evaluating assumptions about quasar variability and cosmological models.

Abstract

In this paper we set out to measure time dilation in quasar light curves. In order to detect the effects of time dilation, sets of light curves from two monitoring programmes are used to construct Fourier power spectra covering timescales from 50 days to 28 years. Data from high and low redshift samples are compared to look for the changes expected from time dilation. The main result of the paper is that quasar light curves do not show the effects of time dilation. Several explanations are discussed, including the possibility that time dilation effects are exactly offset by an increase in timescale of variation associated with black hole growth, or that the variations are caused by microlensing in which case time dilation would not be expected.