= Cosmological horizons in global de Sitter spacetime
{title2=$\chi_p=T+\pi/2,\quad\chi_e=\pi/2-T$}
For a complete comoving observer at the north pole of the <closed slicing of de Sitter spacetime>, radial null rays have $d\chi=\pm dT$. The finite past conformal interval gives the displayed <particle horizon>; the finite remaining future interval gives the displayed <observer event horizon>. The angular distances range strictly between zero and $\pi$ at every finite proper time. Complete constant-$T$ three-spheres are <Cauchy hypersurfaces>, so their domains of dependence cover the global spacetime and they have no <Cauchy horizons>. Cosmological horizons are observer-dependent and are not failures of global hyperbolicity.
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