Title: Sobolev contractivity of the gradient flow maximal function Abstract:  In 2013, Carneiro and Svaiter showed that the heat flow maximal function is contractive in $\dot{W}^{1,2}(\mathbb{R}^n)$ for $W^{1,2}(\mathbb{R}^n)$ functions. In other words, if $K_t$ is the heat kernel then $u_*(x) = \sup_{t > 0} (K_t \ast |f|)(x)$ for some $f \in W^{1,2}(\mathbb{R}^n)$ then $\|\nabla u_*\|_{L^2(\mathbb{R}^n)}