On the exponential convergence to equilibrium for ultrafast diffusion equations

We propose a simple proof of the exponential convergence to equilibrium for ultrafast diffusion equations in ${\mathbb{R}}^n$. Our approach, based on the direct use of Poincar'e inequality, gets rid of the optimal transport arguments used in \cite{fathi2025} which are valid for Gaussian-excluded one-dimensional weights. This simplification allows us to extend their results to Gaussian measures in higher dimensions.