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Unformatted text preview: Differential Geometry 2 Test 2 Define what is meant by a Lie group G and by its Lie algebra g ; define also the exponential map exp : g G . (a) Show that R G : u 7 exp( u ) is the integral curve of g through the identity e G . (b) Prove that there exist open sets (0 3 ) U g and ( e 3 ) V G such that exp is a diffeomorphism from U to V . Note : Smoothness of the exponential map may be assumed. Solutions : A Lie group G is both a group and a smooth manifold, these structures being compatible in the sense that the group operation G G G is a smooth map (inversion G G being also smooth as a consequence). Its Lie algebra g comprises all vector fields on G that are left-invariant; it is a Lie algebra under the usual bracket of vector fields. If g is a left- invariant vector field on G then exp( ) G is defined by exp( ) = (1) where : R G is the (necessarily complete) integral curve of through the identity e ....
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- Spring '09