Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Getting Around Cosmic Variance   Cosmic microwave background (CMB) anisotropies probe the primordial density
field at the edge of the observable Universe. There is a limiting precision
(``cosmic variance'') with which anisotropies can determine the amplitude of
primordial mass fluctuations. This arises because the surface of last scatter
(SLS) probes only a finite two-dimensional slice of the Universe. Probing other
SLSs observed from different locations in the Universe would reduce the cosmic
variance. In particular, the polarization of CMB photons scattered by the
electron gas in a cluster of galaxies provides a measurement of the CMB
quadrupole moment seen by the cluster. Therefore, CMB polarization measurements
toward many clusters would probe the anisotropy on a variety of SLSs within the
observable Universe, and hence reduce the cosmic-variance uncertainty.

35
The categories of this paper are: mtrl-th
28
The categories of this paper are: alg-geom
23
The categories of this paper are: solv-int
27
The categories of this paper are: comp-gas
29
The categories of this paper are: funct-an
3
The categories of this paper are: physics
15
The categories of this paper are: nucl-ex
11
The categories of this paper are: hep-lat
16
The categories of this paper are: stat
2
The categories of this paper are: math
21
The categories of this paper are: adap-org
22
The categories of this paper are: chao-dyn
8
The categories of this paper are: hep-ex
25
The categories of this paper are: patt-sol
1
The categories of this paper are: cs
37
The categories of this paper are: supr-con