2018/03/25 by Bejan, Cornelia-Livia, Nakova, Galia
#53C25 #58B20 #Differential Geometry (math.DG) #FOS: Mathematics
paper · doi:10.48550/arxiv.1803.09213
In this paper we consider a manifold (M,∇ ) with a symmetric linear connection ∇ which induces on the cotangent bundle T^*M of M a semi-Riemannian metric g with a neutral signature. The metric g is called natural Riemann extension and it is a generalization (made by M. Sekizawa and O. Kowalski) of the Riemann extension, introduced by E. K. Patterson and A. G. Walker (1952). We construct two almost para-Hermitian structures on (T^*M, g) which are almost para-Kähler or para-Kähler and prove that the defined almost para-complex structures are harmonic. On certain hypersurfaces of T^*M we construct almost paracontact metric structures, induced by the obtained almost para-Hermitian structures. We determine the classes of the corresponding almost paracontact metric manifolds according to the classification given by S. Zamkovoy and G. Nakova (2018). We obtain a necessary and sufficient condition the considered manifolds to be paracontact metric, K-paracontact metric or para-Sasakian.