Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Bogolyubov Quasiparticles in Constrained Systems   The paper is devoted to the formulation of quantum field theory for an early
universe in General Relativity considered as the Dirac general constrained
system. The main idea is the Hamiltonian reduction of the constrained system in
terms of measurable quantities of the observational cosmology: the world proper
time, cosmic scale factor, and the density of matter. We define " particles" as
field variables in the holomorphic representation which diagonalize the
measurable density. The Bogoliubov quasiparticles are determined by
diagonalization of the equations of motion (but not only of the initial
Hamiltonian) to get the set of integrals of motion (or conserved quantum
numbers, in quantum theory). This approach is applied to describe particle
creation in the models of the early universe where the Hubble parameter goes to
infinity.

4
The categories of this paper are: cond-mat
27
The categories of this paper are: comp-gas
17
The categories of this paper are: q-fin
15
The categories of this paper are: nucl-ex
25
The categories of this paper are: patt-sol
12
The categories of this paper are: nucl-th
24
The categories of this paper are: dg-ga
8
The categories of this paper are: hep-ex
18
The categories of this paper are: econ
26
The categories of this paper are: bayes-an
0
The categories of this paper are: hep-ph
30
The categories of this paper are: q-alg
19
The categories of this paper are: eess
21
The categories of this paper are: adap-org
22
The categories of this paper are: chao-dyn
31
The categories of this paper are: ao-sci