Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A scale at 10 MeV, gravitational topological vacuum, and large extra
  dimensions   We discuss a possible scale of gravitational origin at around $10$ MeV, or
$10^{-12}$ cm, which arises in the MacDowell-Mansouri formalism of gravity due
to the topological Gauss-Bonnet term in the action, as pointed out by Bjorken
several years ago. A length scale of the same size emerges also in the Kodama
solution in gravity, which is known to be closely related to the
MacDowell-Mansouri formulation. We particularly draw attention to the
intriguing incident that existence of six compact extra dimensions originated
from TeV-scale quantum gravity as well points to a length scale of $10^{-12}$
cm, as the compactification scale. The presence of six such extra dimensions is
also in remarkable consistency with the MacDowell-Mansouri formalism; it
provides a possible explanation for the factor of $\sim10^{120}$ multiplying
the Gauss-Bonnet term in the action. We also comment on the relevant
implications of such a scale regarding the thermal history of the universe
motivated by the fact that it is considerably close to $1-2$ MeV below which
the weak interactions freeze out, leading to Big Bang Nucleosynthesis.

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The categories of this paper are: bayes-an
1
The categories of this paper are: cs
19
The categories of this paper are: eess
9
The categories of this paper are: nlin
23
The categories of this paper are: solv-int
22
The categories of this paper are: chao-dyn
35
The categories of this paper are: mtrl-th
4
The categories of this paper are: cond-mat
11
The categories of this paper are: hep-lat
33
The categories of this paper are: plasm-ph
17
The categories of this paper are: q-fin
36
The categories of this paper are: cmp-lg
37
The categories of this paper are: supr-con
31
The categories of this paper are: ao-sci
2
The categories of this paper are: math
10
The categories of this paper are: q-bio