| 11. | The structure group is the orthogonal group.
 
  | 
 | 12. | The circle group is therefore isomorphic to the special orthogonal group SO ( 2 ).
 
  | 
 | 13. | In particular, the space of spinors is a projective representation of the orthogonal group.
 
  | 
 | 14. | The orthogonal group, consisting of all proper and improper rotations, is generated by reflections.
 
  | 
 | 15. | If the gauge symmetry is an orthogonal group then this class is the first Pontrjagin class.
 
  | 
 | 16. | This structure theory is compatible with the action of the pseudo-orthogonal groups plus dilatations.
 
  | 
 | 17. | The Cartan Dieudonn?theorem describes the structure of the orthogonal group for a non-singular form.
 
  | 
 | 18. | Thus reflections generate the orthogonal group, and this result is known as the Cartan Dieudonn?theorem.
 
  | 
 | 19. | The Lie algebra of the generalized orthogonal group o ( 1, n ) is given by matrices
 
  | 
 | 20. | Recall from the previous section that there is a homomorphism from the Clifford group onto the orthogonal group.
 
  |