Dust reverberation mapping in the era of big optical surveys and its
  cosmological application
  The time lag between optical and near-infrared (IR) flux variability can be
taken as a means to determine the sublimation radius of the dusty "torus"
around supermassive black holes in active galactic nuclei (AGN). I will show
that data from big optical survey telescopes, e.g. the Large Synoptic Survey
Telescope (LSST), can be used to measure dust sublimation radii as well. The
method makes use of the fact that the Wien tail of the hot dust emission
reaches into the optical and can be reliably recovered with high-quality
photometry. Simulations show that dust sublimation radii for a large sample of
AGN can be reliably established out to redshift z ~ 0.1-0.2 with the LSST.
Owing to the ubiquitous presence of AGN up to high redshifts, they have been
studies as cosmological probes. Here, I discuss how optically-determined dust
time lags fit into the suggestion of using the dust sublimation radius as a
"standard candle" and propose and extension of the dust time lags as "standard
rulers" in combination with IR interferometry.
