Gradient estimates for a class of elliptic equations with logarithmic terms

We obtain the gradient estimates of the positive solutions to a nonlinear elliptic equation on an n -dimensional complete Riemannian manifold $(M, g)$ ( M , g ) Δ u +au(lnu)ᵖ+bulnu=0, Δ u + a u ( ln u ) p + b u ln u = 0 , where a≠ 0 a ≠ 0 , b are two constants and p=k₁2k₂+1≥ 2 p = k 1 2 k 2 + 1 ≥ 2 , here k₁ k 1 and k₂ k 2 are two positive integers. The gradient bound is independent of the bounds of the solution and the Laplacian of the distance function. As the applications of the estimates, we show the Harnack inequality and the upper bound of the solution.