*** Two-point Correlation Function ***
September 18, 2008: E.Komatsu

Here we provide a program for computing the two-point correlation function,
xi(r), from the power spectrum.

Users may choose to use any of the following input power spectra:

- Linear spectrum in real space
- Linear spectrum in redshift space
- Non-linear spectrum in real space
- Non-linear spectrum in redshift space

The program generates a spherically-averaged two-point correlation function
as a function of R (in units of h^-1 Mpc) given by

xi(R) = int (k^2 dk)/(2 pi^2) P(k) sin(kR)/(kR)

where P(k) is a spherically-averaged power spectrum given by

P(k) = int_0^1 dmu P(k,mu)

For the computation with the linear spectrum, we provide the data for 
the linear power spectrum at z=30, 
"wmap5baosn_max_likelihood_matterpower_at_z=30.dat," which was
generated using CAMB code for the maximum likelihood parameters
given in Table I of Komatsu et al.(2008) [WMAP 5-year interpretation paper] 
with "WMAP5+BAO+SN". The input file for CAMB is also provided 
(wmap5baosn_max_likelihood_params.ini). 

We also provide the data for the non-linear power spectrum,
"wavenumber_pkd11_pkd22_pkd13_at_z=30.txt", computed from
the 3rd-order perturbation theory.

For non-linear power spectrum in redshift space, the power spectra of
velocity divergence fields as well as that of the density-velocity cross 
correlation are required. They are:
"wavenumber_pkt11_pkt22_pkt13_at_z=30.txt", and
"wavenumber_pkdt11_pkdt22_pkdt13_at_z=30.txt", respectively.

- To compile and use the  program, edit Makefile
and simply "./make"
- It will generate executables called "compute_xi".
- Running compute_xi will generate the data file called "Rh_xi.txt".