Geometric structures associated with a contact metric $(\kappa,\mu)$-space

Abstract

We prove that any contact metric $(\kappa,\mu)$-space $(M,\xi,\phi,\eta,g)$ admits a canonical paracontact metric structure which is compatible with the contact form $\eta$. We study such canonical paracontact structure, proving that it verifies a nullity condition and induces on the underlying contact manifold $(M,\eta)$ a sequence of compatible contact and paracontact metric structures verifying nullity conditions. The behavior of that sequence, related to the Boeckx invariant $I_M$ and to the bi-Legendrian structure of $(M,\xi,\phi,\eta,g)$, is then studied. Finally we are able to define a canonical Sasakian structure on any contact metric $(\kappa,\mu)$-space whose Boexkx invariant satisfies $|I_M|>1$.