Eigenvalues and Simplicity of Interval Exchange Transformations

In this paper we consider a class of d-interval exchange transformations, which we call the symmetric class. For this class we define a new self-dual induction process in which the system is successively induced on a union of sub-intervals. This algorithm gives rise to an underlying graph structure which reflects the dynamical behavior of the system, through the Rokhlin towers of the induced maps. The explicit nature of the combinatorial description lends itself well in producing concrete examples having various desired properties. We apply it to build a wide assortment of explicit examples on four intervals having different dynamical properties: these include the first nontrivial examples with eigenvalues (rational or irrational), the first ever example of an exchange on more than three intervals satisfying Veech’s simplicity (though this property was a weakening of the notion of minimal selfjoinings designed in 1982 to be satisfied by interval exchange transformations), and an unexpected example which is non uniquely ergodic, weakly mixing for one invariant ergodic measure but has rational eigenvalues for the other invariant ergodic measure.