Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Bardeen-Petterson Alignment, Jets and Magnetic Truncation in GRMHD
  Simulations of Tilted Thin Accretion Discs   Prevalent around luminous accreting black holes, thin discs are challenging
to resolve in numerical simulations. When the disc and black hole angular
momentum vectors are misaligned, the challenge becomes extreme, requiring
adaptive meshes to follow the disc proper as it moves through the computational
grid. With our new high-performance general relativistic magnetohydrodynamic
(GRMHD) code H-AMR we have simulated the thinnest accretion disc to date, of
aspect ratio $H/R\approx0.03\approx1.7^\circ$ , around a rapidly spinning
($a=0.9375$) black hole, using a cooling function. Initially tilted at
$10^\circ$, the disc warps inside $\sim 5r_g$ into alignment with the black
hole, where $r_g$ is the gravitational radius. This is the first demonstration
of Bardeen-Petterson alignment in MHD with viscosity self-consistently
generated by magnetized turbulence. The disc develops a low-density
high-viscosity ($\alpha_{\rm eff}\sim1.0$) magnetic-pressure--dominated inner
region at $r\lesssim25r_g$ that rapidly empties itself into the black hole.
This inner region may in reality, due to thermal decoupling of ions and
electrons, evaporate into a radiatively inefficient accretion flow if, as we
propose, the cooling time exceeds the accretion time set by the order unity
effective viscosity. We furthermore find the unexpected result that even our
very thin disc can sustain large-scale vertical magnetic flux on the black
hole, which launches powerful relativistic jets that carry $20{-}50\%$ of the
accretion power along the angular momentum vector of the outer tilted disc,
providing a potential explanation for the origin of jets in radio-loud quasars.

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The categories of this paper are: hep-lat
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The categories of this paper are: q-alg
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The categories of this paper are: alg-geom
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The categories of this paper are: hep-th
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The categories of this paper are: funct-an
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The categories of this paper are: eess
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The categories of this paper are: stat
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The categories of this paper are: math-ph
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The categories of this paper are: q-bio
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The categories of this paper are: adap-org
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The categories of this paper are: chem-ph
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The categories of this paper are: nucl-th
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The categories of this paper are: cs
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The categories of this paper are: plasm-ph
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The categories of this paper are: quant-ph
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The categories of this paper are: atom-ph