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t/cosmology2.t  view on Meta::CPAN

# This "module" is written so Doug has something to test against
# for his Astro::Cosmology package

my $nstep = 1e6;
my $_tol = 1/$nstep;

# this routine determines whether or not you have flat universe or
# if you have to use the correction when going between the comoving
# distance and the interesting distances (lum, ang, etc.)

sub _not_flat {

  my $matter = shift;
  my $lambda = shift;

  my $tot = $matter+$lambda;

  if (abs(1-$tot) < $_tol) {
    return(0);
  } elsif ($tot > 1) {
    return(-1); # negative curvature

t/cosmology2.t  view on Meta::CPAN

  $matter = shift if(@_);
  $lambda = shift if(@_);
  $nsteps = shift if(@_);

  # here I have to "correct" the comoving distance depending on the
  # the curvature of the universe.  So, I calculate the curvature,
  # calculate the comoving distance along the line of sight and
  # only then do compute whether the curvature is positive, negatuve
  # or "zero", which means less than the tolerance variable $_tol
  #
  # _not_flat is the routine that checks the curvature, is uses the
  # input lambda and matter, not the computed curvature

  my $curve = 1.0- ($lambda+$matter);
  my $dc = d_c($z,$matter,$lambda,$nsteps);

  if (!_not_flat($matter,$lambda)) {
    return($dc);
  } elsif (_not_flat($matter,$lambda) < 0) {
    # negative curvature
    $curve = abs($curve);
    return(sin($dc*sqrt($curve))/sqrt($curve));
  } else {
    return(sinh($dc*sqrt($curve))/sqrt($curve));
  }

}

=pod

t/cosmology2.t  view on Meta::CPAN

  my $curve = 1.0 - ($lambda + $matter);
  my $sacurve = sqrt(abs($curve));
  my $dm = d_m($z,$matter,$lambda,$nsteps);
  my $vc;

  # this formula is from Carrol, Press and Turner, ARA&Ap, 1992, 30, 499
  # however, it seems odd, as the volume will be negative for negative
  # curvature.

  if (!_not_flat($matter,$lambda)) {

    $vc = $dm**3;
    $vc /= 3.0;

  } elsif (_not_flat($matter,$lambda) < 0) {
    # negative curvature

    $vc = $dm*sqrt(1+$curve*$dm**2) - asin($dm*$sacurve)/$sacurve;
    $vc /= 2*$curve;

  } else {

    $vc = $dm*sqrt(1+$curve*$dm**2) - asinh($dm*$sacurve)/$sacurve;
    $vc /= 2*$curve;