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SUMMARY:How common are misaligned accretion disks around black holes? - Ma
 tthew Liska (Georgia Tech)
DTSTART:20250508T130000Z
DTEND:20250508T140000Z
UID:TALK229882@talks.cam.ac.uk
CONTACT:Loren E. Held
DESCRIPTION:Accretion disks around black holes emit across the electromagn
 etic spectrum\, providing a window into strong-field gravity and extreme p
 lasma environments. By analyzing their light curves and spectra\, astrophy
 sicists aim to probe fundamental questions about relativistic dynamics and
  high-energy astrophysics. Traditionally\, models of black hole accretion 
 have assumed that the disk's angular momentum is aligned with the black ho
 le's spin axis. However\, both observations and theoretical considerations
  increasingly suggest that misalignment—or tilt—is common. In this tal
 k\, I will present new insights from cutting-edge radiative general relati
 vistic magnetohydrodynamic (GRMHD) simulations of tilted accretion disks. 
 These simulations reveal that radiative cooling can induce a dramatic nonl
 inear response: disk warping leads to tearing\, breaking the flow into dis
 crete\, misaligned sub-disks. The resulting dynamics naturally drive disk 
 precession\, which may underlie the quasi-periodic oscillations frequently
  observed in X-ray binaries and active galactic nuclei. In the second part
  of the talk\, I will question the prevailing view that accretion is prima
 rily driven by magnetorotational instability (MRI)-induced turbulence. I w
 ill show that in tilted\, warped disks\, accretion can instead be mediated
  by large-scale hydrodynamic shocks—specifically\, nozzle shocks—offer
 ing a possible explanation for rapid luminosity variability in certain act
 ive galactic nuclei.
LOCATION:MR14 DAMTP and online
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