Cartan's structural equations for singular manifolds

The classical Cartan's structural equations show in a compact way the relation between a connection and its curvature, and reveals their geometric interpretation in terms of moving frames. In order to study the mathematical properties of singularities, we need to study the geometry of manifolds...

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Bibliographic Details
Published in:Balkan journal of geometry and its applications 2014-01, Vol.19 (2), p.118
Main Author: Stoica, Ovidiu Cristinel
Format: Article
Language:English
Subjects:
Analysis
Differential Geometry
Manifolds (Mathematics)
Mathematical Physics
Mathematics
Physics
Structural equation modeling
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Summary:The classical Cartan's structural equations show in a compact way the relation between a connection and its curvature, and reveals their geometric interpretation in terms of moving frames. In order to study the mathematical properties of singularities, we need to study the geometry of manifolds endowed on the tangent bundle with a symmetric bilinear form which is allowed to become degenerate. But if the fundamental tensor is allowed to be degenerate, there are some obstructions in constructing the geometric objects normally associated to the fundamental tensor. Also, local orthonormal frames and coframes no longer exist, as well as the metric connection and its curvature operator. This article shows that, if the fundamental tensor is radical stationary, we can construct in a canonical way geometric objects, determined only by the fundamental form, similar to the connection and curvature forms of Cartan. In particular, if the fundamental tensor is non-degenerate, we obtain the usual connection and curvature forms of Cartan. We write analogs of Cartan's first and second structural equations. As a by product we will find a compact version of the Koszul formula. M.S.C. 2010: 53B30, 53B15, 83C75. Key words: Cartan's structural equations; singular geometry; degenerate manifolds; Koszul formula; Cartan connection; Cartan curvature.
ISSN:1224-2780