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SUMMARY:Exascale simulations of discs around black holes - Yona Lapeyre (E
 NS de Lyon)
DTSTART:20251106T123000Z
DTEND:20251106T133000Z
UID:TALK236122@talks.cam.ac.uk
CONTACT:Mika Kontiainen
DESCRIPTION:Lense-Thirring torque of a spinning black hole causes its accr
 etion disc to warp. This so-called Bardeen-Petterson effect critically inf
 luences the direction and stability of the relativistic jets launched from
  supermassive black holes (SMBH)\, and could explain certain features in h
 igh frequency and type-C quasi periodic oscillations. \n\nHowever\, a lack
  of resolution in numerical simulations previously prevented the further c
 haracterization of such discs. While state-of-the-art simulations use 10 m
 illion SPH particles to reach an effective viscosity alpha of 0.01\, a fac
 tor at least 10 in spatial resolution\, meaning 1\,000 in computational po
 wer\, is required to allow local instabilities to grow. In particular the 
 parametric instability\, which is expected to be a primary physical source
  of wave damping and thus play a major role in the accretion mechanism\, h
 as yet to be captured in a warped disc simulation. Hence\, the size of the
  misaligned region\, the number and width of broken annuli if they exist\,
  and the possibility of an observational signature of the disc bending are
  still to be determined. \n\nDuring the last decade\, GPUs have revolution
 ized the computing capability of supercomputers\, breaking the exascale ba
 rrier (1018 FLOPS) in 2022 with the Frontier cluster. SHAMROCK\, a new ast
 rophysics code published in March 2025\, is one of the codes able to run o
 n such machines. In this talk\, I will present simulations of warped discs
  around SMBH at unprecedented resolutions\, as well as the latest developm
 ents in the SHAMROCK code towards novel theoretical understanding of disc 
 dynamics around black holes.
LOCATION:Institute of Astronomy 
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