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Charles Ehresmann's concepts in differential geometry

Paulette Libermann (2007)

Banach Center Publications

We outline some of the tools C. Ehresmann introduced in Differential Geometry (fiber bundles, connections, jets, groupoids, pseudogroups). We emphasize two aspects of C. Ehresmann's works: use of Cartan notations for the theory of connections and semi-holonomic jets.

Chern classes of vector bundles with singular connections

Guiseppe De Cecco (1982)

Atti della Accademia Nazionale dei Lincei. Classe di Scienze Fisiche, Matematiche e Naturali. Rendiconti Lincei. Matematica e Applicazioni

Si fa vedere che alcune classi di Chern di fibrati vettoriali complessi possono essere costruite non solo partendo da connessioni C ma, sotto certe condizioni, anche da connessioni lineari singolari. Nel caso particolare del fibrato tangente possono essere costruite anche a partire da metriche singolari. Viene fatto uso in modo essenziale della L 2 -coomologia di de Rham (introdotta da Cheeger e Teleman).

Classes caractéristiques exotiques et -connexité des espaces de connexions

Daniel Lehmann (1974)

Annales de l'institut Fourier

Le but de ce travail est double : d’une part, généraliser la construction des classes exotiques pour l’appliquer à d’autres problèmes géométriques que ceux issus des Γ -structures ; d’autre part, préciser, grâce à la notion de J -connexité, remplaçant avantageusement les formules de dérivation utilisées précédemment, l’argument d’invariance homotopique permettant d’obtenir des théorèmes de rigidité, montrant simultanément pourquoi la seule connexité des ensembles de connexions considérés ne suffit...

Classification of principal connections naturally induced on W 2 P E

Jan Vondra (2008)

Archivum Mathematicum

We consider a vector bundle E M and the principal bundle P E of frames of E . Let K be a principal connection on P E and let Λ be a linear connection on M . We classify all principal connections on W 2 P E = P 2 M × M J 2 P E naturally given by K and Λ .

Combinatorial differential geometry and ideal Bianchi–Ricci identities II – the torsion case

Josef Janyška, Martin Markl (2012)

Archivum Mathematicum

This paper is a continuation of [2], dealing with a general, not-necessarily torsion-free, connection. It characterizes all possible systems of generators for vector-field valued operators that depend naturally on a set of vector fields and a linear connection, describes the size of the space of such operators and proves the existence of an ‘ideal’ basis consisting of operators with given leading terms which satisfy the (generalized) Bianchi–Ricci identities without corrections.

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