Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Robertson-Walker fluid sources endowed with rotation characterised by
  quadratic terms in angular velocity parameter   Einstein's equations for a Robertson-Walker fluid source endowed with
rotation Einstein's equations for a Robertson-Walker fluid source endowed with
rotation are presented upto and including quadratic terms in angular velocity
parameter. A family of analytic solutions are obtained for the case in which
the source angular velocity is purely time-dependent. A subclass of solutions
is presented which merge smoothly to homogeneous rotating and non-rotating
central sources. The particular solution for dust endowed with rotation is
presented. In all cases explicit expressions, depending sinusoidally on polar
angle, are given for the density and internal supporting pressure of the
rotating source. In addition to the non-zero axial velocity of the fluid
particles it is shown that there is also a radial component of velocity which
vanishes only at the poles. The velocity four-vector has a zero component
between poles.

9
The categories of this paper are: nlin
22
The categories of this paper are: chao-dyn
10
The categories of this paper are: q-bio
23
The categories of this paper are: solv-int
34
The categories of this paper are: chem-ph
31
The categories of this paper are: ao-sci
18
The categories of this paper are: econ
19
The categories of this paper are: eess
8
The categories of this paper are: hep-ex
27
The categories of this paper are: comp-gas
0
The categories of this paper are: hep-ph
4
The categories of this paper are: cond-mat
35
The categories of this paper are: mtrl-th
20
The categories of this paper are: acc-phys
33
The categories of this paper are: plasm-ph
12
The categories of this paper are: nucl-th