Quantitative gradient estimates for harmonic maps into singular spaces

Harmonic quasi-isometric maps into Gromov hyperbolic ${\rm CAT}(0)$-spaces

“…Suppose the curvature of X is bounded by −b 2 ≤ K X ≤ 0 for some b > 0. By[30, Theorem 1.4], there exists a constant C 1 depending only on r, the dimension n of X, and b such that u is λ-Lipschitz on B(x, r/3) with λ ≤ C 1 • E(u| B(x,s) )…”