Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Phantom behavior via cosmological creation of particles   Recent determinations of the equation of state of dark energy hint that this
may well be of the phantom type, i.e., $w_{de} < -1$. If confirmed by future
experiments, this would strongly point to the existence of fields that violate
the dominant energy condition, which are known to present serious theoretical
difficulties. This paper presents an alternative to this possibility, namely,
that the measured equation of state, $w_{de}$, is in reality an effective one,
the equation of state of the quantum vacuum, $w_{\Lambda} = -1$, plus the
negative equation of state, $w_{c}$, associated to the production of particles
by the gravitational field acting on the vacuum. To illustrate this, three
phenomenological models are proposed and constrained with recent observational
data.

2
The categories of this paper are: math
32
The categories of this paper are: atom-ph
34
The categories of this paper are: chem-ph
18
The categories of this paper are: econ
22
The categories of this paper are: chao-dyn
1
The categories of this paper are: cs
19
The categories of this paper are: eess
35
The categories of this paper are: mtrl-th
24
The categories of this paper are: dg-ga
21
The categories of this paper are: adap-org
17
The categories of this paper are: q-fin
28
The categories of this paper are: alg-geom
37
The categories of this paper are: supr-con
3
The categories of this paper are: physics
26
The categories of this paper are: bayes-an
20
The categories of this paper are: acc-phys