The transition from quasar radio-loud to radio-quiet state in the
  framework of the black hole scalability hypothesis
  There are several lines of evidence that active galactic nuclei (AGN) can be
regarded as scaled-up X-ray binaries (XRB). The timescales of the evolutionary
phenomena in these two classes are proportional to the black hole (BH) masses.
Consequently, unlike in the case of XRBs, the evolution of AGNs is too slow to
be followed directly. What could be done, however, is to assign particular
types of active galaxies to different evolutionary stages observable in XRBs.
We studied such an assignment for three quasars with clear signatures of a
recent transition from the radio-loud to the radio-quiet state. The quasars we
investigated have large-scale radio lobes that are clearly asymmetric -- one
lobe is of Fanaroff-Riley II type, while the other one is a diffuse relic
devoid of a hotspot. We suggest that the prime cause of the asymmetry of these
radio sources is that the nuclei of their host galaxies currently produce no
jets. To prove that, we observed them with milliarcsecond resolution to check
if they are similar to those in radio-quiet quasars. The observations carried
out with the EVN revealed that the nuclei of the quasars under investigation
are not of a core-jet type that is characteristic for radio-loud,
lobe-dominated quasars. It follows that the lobes are no longer fuelled and
that the apparent asymmetry results from the orientation, which causes a time
lag of the order of 10^6 years between their images: the lobe perceived as a
relic is nearer than the lobe with a hotspot and so it is observed in a later
stage of the decay. The three AGNs under investigation were radio-loud earlier,
but now they have switched to the radio-quiet state. In the framework of the
XRB/AGN unification, the above means that they have left the very high state
and have moved now to the high/soft state. (abridged)
