Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Noncommutative cosmological model in the presence of a phantom fluid   We study noncommutative classical Friedmann-Robertson-Walker cosmological
models. The constant curvature of the spatial sections can be positive ($k=1$),
negative ($k=-1$) or zero ($k=0$). The matter is represented by a perfect fluid
with negative pressure, phantom fluid, which satisfies the equation of state $p
=\alpha \rho$ , with $\alpha < - 1$, where $p$ is the pressure and $\rho$ is
the energy density. We use Schutz's formalism in order to write the perfect
fluid Hamiltonian. The noncommutativity is introduced by nontrivial Poisson
brackets between few variables of the models. In order to recover a description
in terms of commutative variables, we introduce variables transformations that
depend on a noncommutative parameter ($\gamma$). The main motivation for the
introduction of the noncommutativity is trying to explain the present
accelerated expansion of the universe. We obtain the dynamical equations for
these models and solve them. The solutions have four constants: $\gamma$, a
parameter associated with the fluid energy $C$, $k$, $\alpha$ and the initial
conditions of the models variables. For each value of $\alpha$, we obtain
different equations of motion. Then, we compare the evolution of the universe
between the present noncommutative models and the corresponding commutative
ones ($\gamma \to 0$). The results show that $\gamma$ is very useful for
describing an accelerating universe. We estimate the value of $\gamma$, for the
present conditions of the Universe. Then, using that value of $\gamma$, in one
of the noncommutative cosmological models, we compute the amount of time this
universe would take to reach the {\it big rip}.

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The categories of this paper are: physics
9
The categories of this paper are: nlin
31
The categories of this paper are: ao-sci
8
The categories of this paper are: hep-ex
35
The categories of this paper are: mtrl-th
26
The categories of this paper are: bayes-an
1
The categories of this paper are: cs
12
The categories of this paper are: nucl-th
17
The categories of this paper are: q-fin
32
The categories of this paper are: atom-ph
34
The categories of this paper are: chem-ph
4
The categories of this paper are: cond-mat
33
The categories of this paper are: plasm-ph
30
The categories of this paper are: q-alg
13
The categories of this paper are: quant-ph
11
The categories of this paper are: hep-lat