De-acceleration s in a homogeneous environment. The long-term effects can be estimated using the relation km s⁻¹ per Gyr as it approximates km² s⁻² kpc⁻¹. The top panel shows the dependence of s on the kinematical parameters of the homogeneous environment: the velocity and velocity dispersion. The magenta point shows the difference between MW gas and stellar disc values. The bottom panel shows the dependence on the SB parameters of collapse speed and scaling, with kinematic parameters v and σ fixed at the magenta point in the top panel. The de-acceleration field can be approximated using Eq. (24).