Gradient estimates and Liouville theorems for exponentially harmonic functions

We study exponentially harmonic functions on complete Riemannian manifolds. Under a lower Ricci curvature bound \(_g≥-Kg\), we first establish a local gradient estimate in terms of the oscillation. We then prove a pointwise gradient estimate for solutions bounded from one side. As an application, when \(_g≥0\), we obtain a Liouville theorem under a one-sided sublinear growth condition. In particular, every exponentially harmonic function bounded above or below is constant.