On roots of dehn twists

Margalit and Schleimer [4] discovered a nontrivial root of the Dehn twist about a nonseparating curve on a closed oriented connected surface. We give a complete set of conjugacy invariants for such a root by using a classification theorem of Matsumoto and Montesinos [5, 6] for pseudo-periodic maps of negative twists. As an application, we determine the range of degree for roots of a Dehn twist.