Anti-Invariant ξ ⊥ -Riemannian Submersions fromAlmost Contact Manifolds

We introduce anti-invariant ξ⊥ -Riemannian submersions from almostcontact manifolds onto Riemannian manifolds. We give an example,investigate the geometry of foliations which are arisen from the definition of a Riemannian submersion and check the harmonicity of suchsubmersions. We also find necessary and sufficient conditions for a special anti-invariant ξ⊥ -Riemannian submersion to be totally geodesic.Moreover, we obtain decomposition theorems for the total manifold ofsuch submersions.