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The density-weighted mean kinematic viscosity isusing $\nu =\alpha p/(\rho \Omega )$. Under the preceding rescaling, letUniqueness of the universal dimensionless solution makes $I_P$ a positive numerical constant independent of $\alpha ,\Omega ,\kappa ,\Sigma ,\mathcal{R}$. HenceFor Keplerian rotation, ${\Omega }^{-2/3}=(GM{)}^{-1/3}r$. The constant-opacity gas-pressure disk viscosity law is thereforeThe particular scaling convention changes the representation of $I_P$ but not this physical law. Its nontrivial powers come from balancing viscous heating, diffusive cooling and vertical support together, rather than assuming a fixed temperature or thickness.