HI as a Probe of the Large Scale Structure in the Post-Reionization
  Universe: Visibility Correlations and Prospects for Detection
  Simulated maps of the HI distribution in the post-reionization era are used
to study the prospects for detection with existing and upcoming radio
telescopes. We consider detection in the redshifted radiation from the
hyperfine transition with a rest frame frequency of 1420 MHz. Possibility of a
statistical detection using visibility correlations is discussed. We show that
the MWA (Murchison Widefield Array) and the GMRT (Giant
  Meterwave Radio Telescope) can potentially detect signal from the HI
distribution at high redshifts. MWA can detect visibility correlations at large
angular scales at all redshifts accessible to it in the post-reionization era.
The GMRT can detect visibility correlations at lower redshifts, specifically
there is a strong case for a survey at z = 1.3. We also discuss prospects for
direct detection of rare peaks in the HI distribution using the GMRT. We show
that direct detection should be possible with integration time that is
comparable to, or even less than, the time required for a statistical
detection. Specifically, it is possible to make a statistical detection of the
HI distribution by measuring the visibility correlation, and, direct detection
of rare peaks in the HI distribution using the GMRT in less than 1000 hours of
observations.
