#### Vol. 290, No. 2, 2017

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The ambient obstruction tensor and conformal holonomy

### Thomas Leistner and Andree Lischewski

Vol. 290 (2017), No. 2, 403–436
##### Abstract

For a conformal manifold, we describe a new relation between the ambient obstruction tensor of Fefferman and Graham and the holonomy of the normal conformal Cartan connection. This relation allows us to prove several results on the vanishing and the rank of the obstruction tensor, for example for conformal structures admitting twistor spinors or normal conformal Killing forms. As our main tool we introduce the notion of a conformal holonomy distribution and show that its integrability is closely related to the exceptional conformal structures in dimensions five and six that were found by Nurowski and Bryant.

##### Keywords
Fefferman–Graham ambient metric, obstruction tensor, conformal holonomy, exceptional conformal structures, normal conformal Killing forms
Primary: 53A30
Secondary: 53C29