Hamilton-Souplet-Zhang’s gradient estimates for two weighted nonlinear parabolic equations

In this paper, we consider gradient estimates for positive solutions to the following weighted nonlinear parabolic equations on a complete smooth metric measure space with only Bakry-E′mery Ricci tensor bounded below: One is u_t=Δ_fu + aulogu+bu with a, b two real constants, and another is u_t = Δ_fu+λu~α with λ, α two real constants. We obtain local Hamilton-Souplet-Zhang type gradient estimates for the above two nonlinear parabolic equations. In particular, our estimates do not depend on any assumption on f.