Comoving gauge in cosmology
= Comoving gauge in cosmology
{title2=$\delta q=0$}
A <comoving gauge in cosmology> chooses hypersurfaces with zero scalar momentum density for the specified fluid or total system. For cold <pressureless matter> it can be implemented by taking the matter velocity potential to vanish. The choice of component must be stated in a multi-fluid system; <density contrasts> on this slicing can differ from those in a Newtonian or spatially flat gauge.