Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Novel approach to the study of quantum effects in the early universe   We develop a theoretical frame for the study of classical and quantum
gravitational waves based on the properties of a nonlinear ordinary
differential equation for a function $\sigma(\eta)$ of the conformal time
$\eta$, called the auxiliary field equation. At the classical level,
$\sigma(\eta)$ can be expressed by means of two independent solutions of the
''master equation'' to which the perturbed Einstein equations for the
gravitational waves can be reduced. At the quantum level, all the significant
physical quantities can be formulated using Bogolubov transformations and the
operator quadratic Hamiltonian corresponding to the classical version of a
damped parametrically excited oscillator where the varying mass is replaced by
the square cosmological scale factor $a^{2}(\eta)$. A quantum approach to the
generation of gravitational waves is proposed on the grounds of the previous
$\eta-$dependent Hamiltonian. An estimate in terms of $\sigma(\eta)$ and
$a(\eta)$ of the destruction of quantum coherence due to the gravitational
evolution and an exact expression for the phase of a gravitational wave
corresponding to any value of $\eta$ are also obtained. We conclude by
discussing a few applications to quasi-de Sitter and standard de Sitter
scenarios.

32
The categories of this paper are: atom-ph
18
The categories of this paper are: econ
19
The categories of this paper are: eess
33
The categories of this paper are: plasm-ph
21
The categories of this paper are: adap-org
10
The categories of this paper are: q-bio
0
The categories of this paper are: hep-ph
16
The categories of this paper are: stat
27
The categories of this paper are: comp-gas
20
The categories of this paper are: acc-phys
1
The categories of this paper are: cs
7
The categories of this paper are: hep-th
17
The categories of this paper are: q-fin
31
The categories of this paper are: ao-sci
24
The categories of this paper are: dg-ga
12
The categories of this paper are: nucl-th