Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Lecture on Quantum Gravity with Perimeter Action and Gravitational
  Singularities   Motivated by quantum-mechanical considerations we earlier suggested an
alternative action for discretised quantum gravity which measures the perimeter
of the space-time and has a dimension of length. It is the so called perimeter
action, since it is a "square root" of the area action in gravity and has a new
constant of dimension one in front. The physical reason to introduce the
perimeter/linear action was to suppress singular configurations "spikes" in the
quantum-mechanical integral over geometries. Here we shall consider the
continuous limit of the discretised perimeter/linear action. We shall
demonstrate that in the modified theory during the time evolution of a large
massive star, when a star undergoes a collapse and develops an event horizon
which confines the light, a smaller space-time region will be created behind
the event horizon which is unreachable by test particles. These regions are
located in the places where a standard theory of gravity has singularities. We
are confronted here with a drastically new concept that during the time
evolution of a massive star a space-time region is created which is excluded
from the physical scene, being physically unreachable by test particles or
observables. If this concept is accepted, then it seems plausible that the
gravitational singularities are excluded from the modified theory.

2
The categories of this paper are: math
0
The categories of this paper are: hep-ph
10
The categories of this paper are: q-bio
23
The categories of this paper are: solv-int
4
The categories of this paper are: cond-mat
1
The categories of this paper are: cs
14
The categories of this paper are: math-ph
30
The categories of this paper are: q-alg
16
The categories of this paper are: stat
9
The categories of this paper are: nlin
31
The categories of this paper are: ao-sci
28
The categories of this paper are: alg-geom
34
The categories of this paper are: chem-ph
32
The categories of this paper are: atom-ph
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The categories of this paper are: mtrl-th
20
The categories of this paper are: acc-phys