Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Microwave background polarization in cosmological models   We introduce a new multipole formalism for polarized radiative transfer in
general spacetime geometries. The polarization tensor is expanded in terms of
coordinate-independent, projected symmetric trace-free (PSTF) tensor-valued
multipoles. The PSTF representation allows us to discuss easily the observer
dependence of the multipoles of the polarization, and to formulate the exact
dynamics of the radiation in convenient 1+3 covariant form. For the case of an
almost-Friedmann-Robertson-Walker (FRW) cosmological model we recast the
Boltzmann equation for the polarization in to a hierarchy of multipole
equations. This allows us to give a rigorous treatment of the generation and
propagation of the polarization of the cosmic microwave background in
almost-FRW models (with open, closed or flat geometries) without recourse to
any harmonic decomposition of the perturbations. We also show how expanding the
intensity and polarization multipoles in derivatives of harmonic functions
gives a streamlined derivation of the mode-expanded multipole hierarchies.
Integral solutions to these hierarchies are provided, and the relation of our
formalism to others in the literature is discussed.

27
The categories of this paper are: comp-gas
30
The categories of this paper are: q-alg
22
The categories of this paper are: chao-dyn
24
The categories of this paper are: dg-ga
0
The categories of this paper are: hep-ph
10
The categories of this paper are: q-bio
21
The categories of this paper are: adap-org
5
The categories of this paper are: gr-qc
25
The categories of this paper are: patt-sol
31
The categories of this paper are: ao-sci
29
The categories of this paper are: funct-an
36
The categories of this paper are: cmp-lg
4
The categories of this paper are: cond-mat
13
The categories of this paper are: quant-ph
20
The categories of this paper are: acc-phys
7
The categories of this paper are: hep-th