Characterization of Riemannian Manifolds with Weak Homology Group G2 (Following A. Gray).
Varietà localmente grassmanniane quaternionali
A previous result characterizing manifolds with a quaternion generalized structure as quaternion local projective manifolds is extended: a manifold admits a quaternion tensorial product structure if and only if it is a quaternion local Grassmannian manifold.
Ancora sulle classi di Stiefel—Whitney dei fibrati quaternionali generalizzati
Founding on the consideration of the inclusion we attain to determine the explicit expression of the Stiefel-Whitney classes of the universal quaternionic generalized fiber bundle by means of a simple system of generators (algebraically independent).
Classi caratteristiche dei fibrati quaternionali generalizzati
This paper is a preliminary note of a for the coming work concerning the generalized quaternion fiber bundle characteristic ring.
Paraquaternionic CR-submanifolds of paraquaternionic Kähler manifolds and semi-Riemannian submersions
In this paper we introduce paraquaternionic CR-submanifolds of almost paraquaternionic hermitian manifolds and state some basic results on their differential geometry. We also study a class of semi-Riemannian submersions from paraquaternionic CR-submanifolds of paraquaternionic Kähler manifolds.
Quaternionic-like structures on a manifold: Note I. 1-integrability and integrability conditions
This Note will be followed by a Note II in these Rendiconti and successively by a wider and more detailed memoir to appear next. Here six quaternionic-like structures on a manifold (almost quaternionic, hypercomplex, unimodular quaternionic, unimodular hypercomplex, Hermitian quaternionic, Hermitian hypercomplex) are defined and interrelations between them are studied in the framework of general theory of G-structures. Special connections are associated to these structures. 1-integrability and...
Quaternionic-like structures on a manifold: Note II. Automorphism groups and their interrelations
We consider different types of quaternionic-like structures. The interrelations between automorphism groups of the subordinated structures and of some admissible connections are studied. A characterization of automorphisms of a quaternionic structure as some kind of projective transformations is given. General results on harmonicity of an automorphism of some -structure are obtained and applied to the case of an almost Hermitian quaternionic structure. Different noteworthy transformations groups...
The rigid body with two controls and the Brockett perturbation.
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