Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Using HI to probe large scale structures at z ~ 3   The redshifted 1420 MHz emission from the HI in unresolved damped
Lyman-\alpha clouds at high z will appear as a background radiation in low
frequency radio observations. This holds the possibility of a new tool for
studying the universe at high-z, using the mean brightness temperature to probe
the HI content and its fluctuations to probe the power spectrum. Existing
estimates of the HI density at z~3 imply a mean brightness temperature of 1 mK
at 320 Mhz. The cross-correlation between the temperature fluctuations across
different frequencies and sight lines is predicted to vary from 10^{-7} K^2 to
10^{-8} K^2 over intervals corresponding to spatial scales from 10 Mpc to 40
Mpc for some of the currently favoured cosmological models. Comparing this with
the expected sensitivity of the GMRT, we find that this can be detected with
\~10 hrs of integration, provided we can distinguish it from the galactic and
extragalactic foregrounds which will swamp this signal. We discuss a strategy
based on the very distinct spectral properties of the foregrounds as against
the HI emission, possibly allowing the removal of the foregrounds from the
observed maps.

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The categories of this paper are: chem-ph
25
The categories of this paper are: patt-sol
9
The categories of this paper are: nlin
28
The categories of this paper are: alg-geom
8
The categories of this paper are: hep-ex
0
The categories of this paper are: hep-ph
4
The categories of this paper are: cond-mat
17
The categories of this paper are: q-fin
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The categories of this paper are: eess
29
The categories of this paper are: funct-an
11
The categories of this paper are: hep-lat
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The categories of this paper are: plasm-ph
27
The categories of this paper are: comp-gas
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The categories of this paper are: math
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The categories of this paper are: quant-ph
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The categories of this paper are: cs