Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Fermi-bounce Cosmology and scale invariant power-spectrum   We develop a non-singular bouncing cosmology using a non-trivial coupling of
general relativity to fermionic fields. The usual Big Bang singularity is
avoided thanks to a negative energy density contribution from the fermions. Our
theory is ghost-free since the fermionic operator that generates the bounce is
equivalent to torsion, which has no kinetic terms. The physical system consists
of standard general relativity plus a topological sector for gravity, and
fermionic matter described by Dirac fields with a non-minimal coupling. We show
that a scale invariant power-spectrum generated in the contracting phase can be
recovered by suitable choices of fermion number density and bare mass, thus
providing a possible alternative to the inflationary scenario.

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The categories of this paper are: math
37
The categories of this paper are: supr-con
26
The categories of this paper are: bayes-an
23
The categories of this paper are: solv-int
35
The categories of this paper are: mtrl-th
0
The categories of this paper are: hep-ph
14
The categories of this paper are: math-ph
1
The categories of this paper are: cs
29
The categories of this paper are: funct-an
19
The categories of this paper are: eess
18
The categories of this paper are: econ
27
The categories of this paper are: comp-gas
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The categories of this paper are: hep-ex
28
The categories of this paper are: alg-geom
34
The categories of this paper are: chem-ph
31
The categories of this paper are: ao-sci