Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Semiclassical approach for the evaporating black hole revisited   A recent calculation shows that the observed energy density in the Unruh
state at the future event horizon as seen by a freely falling observer is
finite if the observer is released from rest at any positive distance outside
the horizon; however, it is getting larger and larger so that it is negatively
divergent at the horizon in the limit that the observer starts falling from
rest at the horizon, which corresponds to the infinite boost with respect to
the freely falling observer at a finite distance from the horizon. In order to
resolve some conflicts between the recent calculation and the conventional ones
in the well-known literatures, the calculation of the free-fall energy density
is revisited and some differences are pointed out.

2
The categories of this paper are: math
31
The categories of this paper are: ao-sci
26
The categories of this paper are: bayes-an
35
The categories of this paper are: mtrl-th
27
The categories of this paper are: comp-gas
6
The categories of this paper are: astro-ph
20
The categories of this paper are: acc-phys
16
The categories of this paper are: stat
12
The categories of this paper are: nucl-th
4
The categories of this paper are: cond-mat
37
The categories of this paper are: supr-con
29
The categories of this paper are: funct-an
9
The categories of this paper are: nlin
28
The categories of this paper are: alg-geom
19
The categories of this paper are: eess
17
The categories of this paper are: q-fin