3-Sasakian manifolds, 3-cosymplectic manifolds and Darboux theorem

摘要

We present a compared analysis of some properties of 3-Sasakian and 3-cosymplectic manifolds. We construct a canonical\udconnection on an almost 3-contact metric manifold which generalises the Tanaka–Webster connection of a contact metric manifold\udand we use this connection to show that a 3-Sasakian manifold does not admit any Darboux-like coordinate system. Moreover, we\udprove that any 3-cosymplectic manifold is Ricci-flat and admits a Darboux coordinate system if and only if it is flat.