2 3 Fe b 20 06 HARMONIC ALMOST CONTACT STRUCTURES
نویسندگان
چکیده
An almost contact metric structure is parametrized by a section σ of an associated homogeneous fibre bundle, and conditions for σ to be a harmonic section, and a harmonic map, are studied. These involve the characteristic vector field ξ, and the almost complex structure in the contact subbundle. Several examples are given where the harmonic section equations for σ reduce to those for ξ, regarded as a section of the unit tangent bundle. These include trans-Sasakian structures, and certain nearly cosymplectic structures. On the other hand, we obtain examples where ξ is harmonic but σ is not a harmonic section. Many of our examples arise by considering hypersurfaces of almost Her-mitian manifolds, with the induced almost contact structure, and comparing the harmonic section equations for both structures.
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