Transverse comoving distance
= Transverse comoving distance
{title2=$D_M=(1+z)D_A$}
The distance that converts a small angular separation into a transverse <comoving distance> at a specified <cosmological redshift>. It equals the radial comoving distance in spatially flat geometry; <cosmological spatial curvature> changes that equality. A comoving acoustic ruler has angular size $r_d/D_M$.