Coherent emission and the escape of high brightness temperature radiation in active galactic nuclei

High brightness temperatures (T-b) implied by quasar intraday variability may be explained by coherent emission, or else by physically implausible bulk relativistic Lorentz factors Gamma greater than or equal to 100. Previous theory asserts that various absorption mechanisms will block escape of such coherent, high-brightness sources. Yet this same theory fails to account for laboratory experiments detecting collective emission. Probably this is because present theory is inadequate, and should not be used to rule out collective radiation processes.