Wednesday Colloquium


"Broad-emission-line radio galaxies provide challenges to jet production theories"

Marek Sikora (NCAC, Warsaw)

Accretion onto supermassive black holes located in broad-emission-line radio galaxies (BLRGs) is predicted by theory to proceed via geometrically very thin accretion disks, which makes them most challenging objects regarding their ability to produce powerful jets. As recent numerical simulations indicate, even the magnetically-arrested-disk (MAD) scenario is not able to reproduce the jet power observed in these objects - those are measured to approach and sometimes even exceed the accretion luminosities. We discuss possible origins of this discrepancy and argue that it is most likely due to inappropriate approximations used to treat optically thick, radiatively efficient accretion disks within the MAD-zone.


"Superfluid vortex avalanches and pulsar glitches"

George Howitt (University of Melbourne)

Rotating neutron stars, or pulsars, are famously stable objects whose rotation periods lengthen over time. Some pulsars, however, experience sudden spin up events, known as glitches. It is widely believed that the cause of glitches is a sudden rearrangement of superfluid vortices in the neutron star interior, but the diverse phenomenology of glitches coupled with a lack of observational data makes this a difficult model to test. I will discuss work that tests the validity of the superfluid avalanche glitch model in observational data and numerical experiments.


"What was the last Nobel Prize in Physics given for?"

Marek Napiórkowski (Institute for Theoretical Physics, Warsaw University)