Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Black Shells, Dirac's Field and the species problem   We describe a thermal atmosphere around a black hole as vacuum excitations
near to gravitational radius of a contracting thin black shell, i.e., in terms
of properties of the physical vacuum of fields around a thin shell of mass $M$
collapsing from infinity to the Schwarzschild radius according to an external
stationary observer. A natural explanation is introduced for the necessary
cutoff using the equations of motion of the shells. We make a thermodynamic
description of a fermionic field near the gravitational radius. Then a solution
to the species problem for two fields, scalar one and spinor one, is proposed.
Finally we get the Bekenstein-Hawking entropy as entanglement entropy of a
thermal atmosphere, independent from number of fields.

36
The categories of this paper are: cmp-lg
1
The categories of this paper are: cs
17
The categories of this paper are: q-fin
20
The categories of this paper are: acc-phys
19
The categories of this paper are: eess
16
The categories of this paper are: stat
25
The categories of this paper are: patt-sol
8
The categories of this paper are: hep-ex
30
The categories of this paper are: q-alg
29
The categories of this paper are: funct-an
23
The categories of this paper are: solv-int
22
The categories of this paper are: chao-dyn
28
The categories of this paper are: alg-geom
4
The categories of this paper are: cond-mat
26
The categories of this paper are: bayes-an
35
The categories of this paper are: mtrl-th