Schwarz lemma for real harmonic functions onto surfaces with non-negative Gaussian curvature

David Kalaj, Miodrag Mateljević, Iosif Pinelis

Assume that $f$ is a real $\rho$-harmonic function of the unit disk $\mathbb{D}$ onto the interval $(-1,1)$, where $\rho (u,v)=R(u)$ is a metric defined in the infinite strip $(-1,1)\time…