NumCosmoDistancebao_A_scale

This function returns the BAO $A$ parameter. It is defined as $$ A \equiv D_V (z) \frac{\sqrt{\Omega_{m0} H_0^2}}{z c},$$ where $\Omega_{m0}$ is the matter density parameter [nc_hicosmo_Omega_m0()], $c$ is the speed of light [ncm_c_c()], $H_0$ is the Hubble parameter [nc_hicosmo_H0()] and $D_V(z)$ is the dilation scale [nc_distance_dilation_scale()]. See Section 4.5 from [Eisenstein et al. (2005)][XEisenstein2005] [arXiv].