Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Dead Zone Formation and Nonsteady Hyperaccretion in Collapsar Disks : A
  Possible Origin of Short-Term Variability in the Prompt Emission of Gamma-Ray
  Bursts   The central engine of gamma-ray bursts (GRBs) is believed to be a hot and
dense disk with hyperaccretion onto a few solar-mass black hole. We investigate
where the magnetorotational instability (MRI) actively operates in the
hyperaccretion disk, which can cause angular momentum transport in the disk.
The inner region of hyperaccretion disks can be neutrino opaque, and the
energy- and momentum-transport by neutrinos could affect the growth of the MRI
significantly. Assuming reasonable disk models and a weak magnetic field $B
\lesssim 10^{14} \rm{G}$, it is found that the MRI is strongly suppressed by
the neutrino viscosity in the inner region of hyperaccretion disks. On the
other hand, the MRI can drive active MHD turbulence in the outer
neutrino-transparent region regardless of the field strength. This suggests
that the baryonic matter is accumulated into the inner dead zone where the MRI
grows inactively and the angular momentum transport is inefficient. When the
dead zone gains a large amount of mass and becomes gravitationally unstable,
intense mass accretion onto the central black hole would occur episodically
through the gravitational torque. This process can be a physical mechanism of
the short-term variability in the prompt emission of GRBs. Finally, the origin
of flaring activities in the X-ray afterglow is predicted in the context of our
episodic accretion scenario.

8
The categories of this paper are: hep-ex
26
The categories of this paper are: bayes-an
24
The categories of this paper are: dg-ga
5
The categories of this paper are: gr-qc
23
The categories of this paper are: solv-int
35
The categories of this paper are: mtrl-th
34
The categories of this paper are: chem-ph
20
The categories of this paper are: acc-phys
30
The categories of this paper are: q-alg
4
The categories of this paper are: cond-mat
31
The categories of this paper are: ao-sci
9
The categories of this paper are: nlin
22
The categories of this paper are: chao-dyn
2
The categories of this paper are: math
33
The categories of this paper are: plasm-ph
17
The categories of this paper are: q-fin