kruskal diagram

0_generate-kruskal.d

import std;

enum C = 299792458;

void main()
{
    for (int i = -3; i <= 3; ++i) {
        double t = 2.5e-9*i;
        double a = tanh(C*t/2.);
        "  t*100, t*100*%f title \"t=%2fe-9\" lc rgb \"red\",  \\".writefln(a, i*2.5);
        "  t*100*%f, t*100 notitle lc rgb \"red\",  \\".writefln(a);
    }
    for (int i = 0; i < 2; ++i) {
        double r = i*.5;
        double a = (r-1)*exp(r);
        "  %f*tan(t), %f/cos(t) title \"r=%f\" lc rgb \"blue\",  \\".writefln(-a, -a, r);
    }
    for (int i = 0; i < 4; ++i) {
        double r = i*.1+1.1;
        double a = (r-1)*exp(r);
        "  %f/cos(t), %f*tan(t) title \"r=%f\" lc rgb \"blue\",  \\".writefln(a, a, r);
    }
    "  t*100, t*100 title \"t=+inf\" lw 2 lc rgb \"black\",  \\".writefln();
    "  t*100, -t*100 title \"t=-inf\" lw 2 lc rgb \"black\",  \\".writefln();
}

plot.plt

set size square

set xrange [-2:2]
set yrange [-2:2]
set parametric
set samples 1000
set key outside
set notics

plot  \
  t*100, t*100*-0.809032 title "t=-7.500000e-9" lc rgb "red",  \
  t*100*-0.809032, t*100 notitle lc rgb "red",  \
  t*100, t*100*-0.634839 title "t=-5.000000e-9" lc rgb "red",  \
  t*100*-0.634839, t*100 notitle lc rgb "red",  \
  t*100, t*100*-0.358131 title "t=-2.500000e-9" lc rgb "red",  \
  t*100*-0.358131, t*100 notitle lc rgb "red",  \
  t*100, t*100*0.000000 title "t=0.000000e-9" lc rgb "red",  \
  t*100*0.000000, t*100 notitle lc rgb "red",  \
  t*100, t*100*0.358131 title "t=2.500000e-9" lc rgb "red",  \
  t*100*0.358131, t*100 notitle lc rgb "red",  \
  t*100, t*100*0.634839 title "t=5.000000e-9" lc rgb "red",  \
  t*100*0.634839, t*100 notitle lc rgb "red",  \
  t*100, t*100*0.809032 title "t=7.500000e-9" lc rgb "red",  \
  t*100*0.809032, t*100 notitle lc rgb "red",  \
  1.000000*tan(t), 1.000000/cos(t) title "r=0.000000" lc rgb "blue",  \
  0.824361*tan(t), 0.824361/cos(t) title "r=0.500000" lc rgb "blue",  \
  0.300417/cos(t), 0.300417*tan(t) title "r=1.100000" lc rgb "blue",  \
  0.664023/cos(t), 0.664023*tan(t) title "r=1.200000" lc rgb "blue",  \
  1.100789/cos(t), 1.100789*tan(t) title "r=1.300000" lc rgb "blue",  \
  1.622080/cos(t), 1.622080*tan(t) title "r=1.400000" lc rgb "blue",  \
  t*100, t*100 title "t=+inf" lw 2 lc rgb "black",  \
  t*100, -t*100 title "t=-inf" lw 2 lc rgb "black"

I added captions using Inkscape.