Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Is it possible to observationally distinguish adiabatic Quartessence
  from LambdaCDM?   The equation of state (EOS) in quartessence models interpolates between two
stages: $p\simeq 0$ at high energy densities and $p\approx -\rho$ at small
ones. In the quartessence models analyzed up to now, the EOS is convex,
implying increasing adiabatic sound speed ($c_{s}^{2}$) as the energy density
decreases in an expanding Universe. A non-negligible $c_{s}^{2}$ at recent
times is the source of the matter power spectrum problem that plagued all
convex (non-silent) quartessence models. Viability for these cosmologies is
only possible in the limit of almost perfect mimicry to $\Lambda$CDM. In this
work we investigate if similarity to $\Lambda$CDM is also required in the class
of quartessence models whose EOS changes concavity as the Universe evolves. We
focus our analysis in the simple case in which the EOS has a step-like shape,
such that at very early times $p\simeq0$, and at late times $p\simeq const<0$.
For this class of models a non-negligible $c_{s}^{2}$ is a transient
phenomenon, and could be relevant only at a more early epoch. We show that
agreement with a large set of cosmological data requires that the transition
between these two asymptotic states would have occurred at high redshift
($z_t\gtrsim38$). This leads us to conjecture that the cosmic expansion history
of any successful non-silent quartessence is (practically) identical to the
$\Lambda$CDM one.

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The categories of this paper are: physics
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The categories of this paper are: chao-dyn
28
The categories of this paper are: alg-geom
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The categories of this paper are: funct-an
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The categories of this paper are: nucl-ex
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The categories of this paper are: q-fin
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The categories of this paper are: adap-org
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The categories of this paper are: ao-sci
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The categories of this paper are: solv-int
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The categories of this paper are: gr-qc
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The categories of this paper are: patt-sol
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The categories of this paper are: econ
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The categories of this paper are: chem-ph
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The categories of this paper are: comp-gas
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The categories of this paper are: hep-ex
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The categories of this paper are: cond-mat