Ricci almost soliton and almost Yamabe soliton on Kenmotsu manifold
Abstract
We prove that a Ricci almost soliton on a Kenmotsu manifold of dimension >3 reduces to an expanding Ricci soliton satifying certain condition on the potential vector field or on the soliton function. Next, we show that any Ricci almost soliton on a Kenmotsu manifold is trivial (Einstein) if the soliton vector leaves the contact form η invariant. Finally, we classify (locally) a Kenmotsu manifold admitting an almost Yamabe soliton. Some examples have been constructed of almost Yamabe solitons on different class of warped product spaces.
Communicated by L. W. Tu