Past incompleteness of the expanding flat slicing of de Sitter spacetime (source code)

= Past incompleteness of the expanding flat slicing of de Sitter spacetime
{c}

The geodesic with nonzero conserved spatial momentum reaches $t=-\infty$ after the finite past proper time
$$
\tau_-=-\frac1{2H}\log\frac{\sqrt{1+v_0^2}+1}{\sqrt{1+v_0^2}-1}.
$$
This is incompleteness of the expanding coordinate patch, whose geodesics extend smoothly in global <de Sitter spacetime>; it is not a curvature singularity.