Teichmüller curves,Galois actions and $ \widehat {GT} $‐relations

Teichmüller curves are geodesic discs in Teichmüller space that project to algebraic curves C in the moduli space M_g. Some Teichmüller curves can be considered as components of Hurwitz spaces. We show that the absolute Galois group G_? acts faithfully on the set of these embedded curves. We also compare the action of G_? on π₁(C) with the one on π₁(M_g) and obtain a relation in the Grothendieck–Teichmüller group, seemingly independent of the known ones. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)