Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Dust-filled axially symmetric universes with a cosmological constant   Following the recent recognition of a positive value for the vacuum energy
density and the realization that a simple Kantowski-Sachs model might fit the
classical tests of cosmology, we study the qualitative behavior of three
anisotropic and homogeneous models: Kantowski-Sachs, Bianchi type-I and Bianchi
type-III universes, with dust and a cosmological constant, in order to find out
which are physically permitted. We find that these models undergo
isotropization up to the point that the observations will not be able to
distinguish between them and the standard model, except for the Kantowski-Sachs
model $(\Omega_{k_{0}}<0)$ and for the Bianchi type-III $(\Omega_{k_{0}}>0)$
with $\Omega_{\Lambda_{0}}$ smaller than some critical value
$\Omega_{\Lambda_{M}}$. Even if one imposes that the Universe should be nearly
isotropic since the last scattering epoch ($z\approx 1000$), meaning that the
Universe should have approximately the same Hubble parameter in all directions
(considering the COBE 4-Year data), there is still a large range for the matter
density parameter compatible with Kantowsky-Sachs and Bianchi type-III if
$|\Omega_0+\Omega_{\Lambda_0}-1|\leq \delta$, for a very small $\delta$ . The
Bianchi type-I model becomes exactly isotropic owing to our restrictions and we
have $\Omega_0+\Omega_{\Lambda_0}=1$ in this case. Of course, all these models
approach locally an exponential expanding state provided the cosmological
constant $\Omega_\Lambda>\Omega_{\Lambda_{M}}$.

0
The categories of this paper are: hep-ph
37
The categories of this paper are: supr-con
22
The categories of this paper are: chao-dyn
7
The categories of this paper are: hep-th
15
The categories of this paper are: nucl-ex
24
The categories of this paper are: dg-ga
26
The categories of this paper are: bayes-an
36
The categories of this paper are: cmp-lg
25
The categories of this paper are: patt-sol
20
The categories of this paper are: acc-phys
3
The categories of this paper are: physics
27
The categories of this paper are: comp-gas
16
The categories of this paper are: stat
28
The categories of this paper are: alg-geom
11
The categories of this paper are: hep-lat
12
The categories of this paper are: nucl-th