use strict;
use Svg;
use Math::Trig qw(sinh cosh acos asinh acosh pi);
sub ScaleFunc {
my ($H0, $M0, $with_lambda) = @_;
if ($M0 == 1) {
my $q0 = 2/(3*$H0);
return sub { my ($q) = @_; ($q - $q0, (1.5 * $H0 * $q) ** (2/3)) };
}
if ($with_lambda) {
my $L0 = 1 - $M0;
# assume 0 < $M0 < 1
my $a = ($M0/$L0) ** (1/3);
my $b = 1.5 * $H0 * sqrt($L0);
my $q0 = asinh(sqrt($L0/$M0)) / $b;
return sub { my ($q) = @_; ($q - $q0, $a * (sinh($b * $q) ** (2/3))) }
} else {
# \Omega_{\Lambda_0} = 0
my $k0 = 1 - $M0;
if ($M0 == 0) {
return sub { my ($q) = @_; ($q - 1/$H0, $q * $H0) }
} else {
my $a = $M0 / (2 * abs($k0));
my $b = 1 / ($H0 * sqrt(abs($k0)));
my $c = $a * $b;
if ($M0 > 1) {
my $d = $a * (2 / ($H0 * $M0) - acos(2/$M0 - 1) * $b);
return sub { my ($q) = @_; ($c * ($q - sin($q)) + $d, $a * (1 - cos($q))) }
} else {
# 0 < M < 1
my $d = $a * (acosh(2/$M0 - 1) * $b - 2 / ($H0 * $M0));
return sub { my ($q) = @_; ($c * (sinh($q) - $q) + $d, $a * (cosh($q) - 1)) }
}
}
}
}
sub SubscriptedText {
my $text = shift;
$text->add(shift);
my $sub = 0;
for my $t (@_) {
$sub = !$sub;
$text->tspan($sub ? (dy => 4, 'font-size' => 12) : (dy => -4))->add($t);
}
}
my ($image_width,$image_height) = (620,500);
my ($origin_x, $origin_y) = (30.5,450.5);
my $pad_right = 70;
my ($tlo, $thi, $ahi) = (-15,18,2.5);
my $svg = new Svg(width => $image_width, height => $image_height);
# $svg->rect(width => $image_width, height => $image_height, fill => 'gray');
$svg->defs()->marker(id => 'arrowhead', refX => 0, refY => 3, markerWidth => 10, markerHeight => 6, markerUnits => 'userSpaceOnUse', orient => 'auto')->path(d => 'M 0,0 L 10,3 L 0,6 z');
my $traces = $svg->group(stroke => 'black', 'stroke-width' => 2, fill => 'none');
my $axes = $svg->group(stroke => 'black', 'stroke-width' => 1, fill => 'none');
my $labels = $svg->group('font-family' => 'Nimbus Roman No9 L, Times, serif', 'font-size' => 20, 'text-anchor' => 'middle', stroke => 'none', fill => 'black');
my $H0 = 1 / 13.95;
my $M0 = 0.279;
my ($graphscalex,$graphscaley) = (($image_width-$origin_x-$pad_right)/($thi-$tlo), -$origin_y/$ahi);
my ($graphofsx,$graphofsy) = ($origin_x - $tlo * $graphscalex, $origin_y);
for my $z ([0,0,30,'none'],[$M0,0,3.17,'1,4'],[1,0,26,'2,2'],[6,0,2*pi,'1,3,4,3'],[$M0,1,27,'5,3']) {
my ($m0,$with_lambda,$max_q,$dashes) = @$z;
my $f = ScaleFunc($H0,$m0,$with_lambda);
my (@x,@y);
for my $i (0..200) {
($x[$i],$y[$i]) = &$f($i / 200 * $max_q);
}
$traces->path('stroke-dasharray' => $dashes, ($m0 == 6 ? () : ('marker-end' => 'url(#arrowhead)')), d => MakePath(\@x, \@y, $graphscalex, $graphscaley, $graphofsx, $graphofsy, 1));
}
$axes->line(x1 => $origin_x, y1 => $image_height-20, x2 => $origin_x, y2 => 20, 'marker-end' => 'url(#arrowhead)');
$axes->line(x1 => 10, y1 => $origin_y, x2 => $image_width - $pad_right + 10, y2 => $origin_y, 'marker-end' => 'url(#arrowhead)');
$labels->text(x => ($origin_x + $image_width) / 2, y => $image_height-10)->add('Billions of years from now');
my $path = '';
for my $gyr (-13.7, -10, -5, 0, 5, 10, 15) {
my $x = int($gyr * $graphscalex + $graphofsx);
my $y = $origin_y-5;
$path .= "M$x.5,${y}l0,10";
$labels->text(x => $x, y => $origin_y + 20)->add($gyr);
}
$axes->path(d => $path);
$labels->circle(cx => $graphofsx, cy => $graphscaley + $graphofsy, r => 4);
$labels->text(x => $graphofsx-5, y => $graphscaley + $graphofsy, 'text-anchor' => 'end')->add('Now');
$labels->text()->rotate(-90)->translate($origin_x - 8, $origin_y / 2)->add("Average distance between galaxies");
my $trace_labels = $labels->group('font-family' => 'DejaVu Serif, serif', 'font-size' => 16);
SubscriptedText($trace_labels->text(x => 465, y => 30, 'text-anchor' => 'end'), "\x{3A9}", 'M', " = 0.3, \x{3A9}", "\x{39B}", " = 0.7");
SubscriptedText($trace_labels->text(x => 520, y => 50, 'text-anchor' => 'start'), "\x{3A9}", 'M', ' = 0');
SubscriptedText($trace_labels->text(x => 535, y => 70, 'text-anchor' => 'start'), "\x{3A9}", 'M', ' = 0.3');
SubscriptedText($trace_labels->text(x => 540, y => 95, 'text-anchor' => 'start'), "\x{3A9}", 'M', ' = 1');
SubscriptedText($trace_labels->text(x => 540, y => 400, 'text-anchor' => 'start'), "\x{3A9}", 'M', ' = 6');
$svg->write('Friedmann universes.svg');