Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Rip/singularity free cosmology models with bulk viscosity   In this paper we present two concrete models of non-perfect fluid with bulk
viscosity to interpret the observed cosmic accelerating expansion phenomena,
avoiding the introduction of exotic dark energy. The first model we inspect has
a viscosity of the form ${\zeta} = {\zeta}_0 + ({\zeta}_1-{\zeta}_2q)H$ by
taking into account of the decelerating parameter q, and the other model is of
the form ${\zeta} = {\zeta}_0 + {\zeta}_1H + {\zeta}_2H^2$. We give out the
exact solutions of such models and further constrain them with the latest
Union2 data as well as the currently observed Hubble-parameter dataset (OHD),
then we discuss the fate of universe evolution in these models, which confronts
neither future singularity nor little/pseudo rip. From the resulting curves by
best fittings we find a much more flexible evolution processing due to the
presence of viscosity while being consistent with the observational data in the
region of data fitting. With the bulk viscosity considered, a more realistic
universe scenario is characterized comparable with the {\Lambda}CDM model but
without introducing the mysterious dark energy.

17
The categories of this paper are: q-fin
27
The categories of this paper are: comp-gas
37
The categories of this paper are: supr-con
16
The categories of this paper are: stat
1
The categories of this paper are: cs
10
The categories of this paper are: q-bio
25
The categories of this paper are: patt-sol
8
The categories of this paper are: hep-ex
20
The categories of this paper are: acc-phys
23
The categories of this paper are: solv-int
24
The categories of this paper are: dg-ga
32
The categories of this paper are: atom-ph
21
The categories of this paper are: adap-org
4
The categories of this paper are: cond-mat
31
The categories of this paper are: ao-sci
34
The categories of this paper are: chem-ph