Nonaccreting similarity disk supplied by an inner torque ($M=\mathrm{const},J\propto t^{1/4},\mathcal{G}(0)\propto t^{-3/4}$)

The $a=5/4$ compact self-similar disk with density-linear viscosity has outward drift $r/(2t)$ but zero limiting mass flux at the origin. Its viscous torque in an accretion disk has a positive finite inner limit for $t>0$, equal to $dJ/dt$. Thus disk mass conservation coexists with growth of angular momentum; an external central torque supplies that growth.