Let S be a compact surface - or the interior of a compact surface - and let V be the manifold of cooriented contact elements of S equiped with its canonical contact structure. A diffeomorphism of V that preserves the contact structure and its coorientation is called a contact transformation over S. We prove the following results. 1) If S is neither a sphere nor a torus then the inclusion of the diffeomorphism group of S into the contact transformation group is 0-connected. 2) If S is a sphere then the contact transformation group is connected. 3) if S is a torus then the homomorphism from the contact transformation group of S to the automorphism group of $H_1(V) \\simeq Z^3$ has connected fibers and the image is (known to be) the stabilizer of $Z^2 \\times \\{0\\}$).
@article{ISBN: 2-940264-05-8,
author = {Giroux, Emmanuel},
title = {Sur les transformations de contact au-dessus des surfaces},
journal = {HAL},
volume = {2001},
number = {0},
year = {2001},
language = {fr},
url = {http://dml.mathdoc.fr/item/ISBN: 2-940264-05-8}
}
Giroux, Emmanuel. Sur les transformations de contact au-dessus des surfaces. HAL, Tome 2001 (2001) no. 0, . http://gdmltest.u-ga.fr/item/ISBN:%202-940264-05-8/