“…where ∆ f R = ∆R− < ∇f, ∇R >, λ i are the eigenvalues of Ricci tensor. Then the scalar curvature must be constant (this result also can be obtained from the main result in the author and Ge's paper [10]), implies that the scalar curvature and the Ricci curvature must be zero, hence (M, g, f ) is the Gaussian soliton. Without the assumption of nonnegative Ricci curvature, Munteanu and Wang [14] proved that if |Ric| ≤ 1 100n , then (M, g, f ) is isometric to the Gaussian soliton.…”