Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Dynamics of the four kinds of Trapping Horizons and Existence of Hawking
  Radiation   We work with the notion of apparent/trapping horizons for spherically
symmetric, dynamical spacetimes: these are quasi-locally defined, simply based
on the behaviour of congruence of light rays. We show that the sign of the
dynamical Hayward-Kodama surface gravity is dictated by the inner/outer nature
of the horizon. Using the tunneling method to compute Hawking Radiation, this
surface gravity is then linked to a notion of temperature, up to a sign that is
dictated by the future/past nature of the horizon. Therefore two sign effects
are conspiring to give a positive temperature for the black hole case and the
expanding cosmology, whereas the same quantity is negative for white holes and
contracting cosmologies. This is consistent with the fact that, in the latter
cases, the horizon does not act as a separating membrane, and Hawking emission
should not occur.

11
The categories of this paper are: hep-lat
1
The categories of this paper are: cs
18
The categories of this paper are: econ
2
The categories of this paper are: math
12
The categories of this paper are: nucl-th
36
The categories of this paper are: cmp-lg
23
The categories of this paper are: solv-int
16
The categories of this paper are: stat
26
The categories of this paper are: bayes-an
20
The categories of this paper are: acc-phys
33
The categories of this paper are: plasm-ph
19
The categories of this paper are: eess
32
The categories of this paper are: atom-ph
37
The categories of this paper are: supr-con
30
The categories of this paper are: q-alg
3
The categories of this paper are: physics