Link to this article: http://journals.cambridge.org/abstract_S0143385716000262How to cite this article: DAVID AULICINO Afne invariant submanifolds with completely degenerate Kontsevich-Zorich spectrum.Abstract. We prove that if the Lyapunov spectrum of the Kontsevich-Zorich cocycle over an affine SL 2 (R)-invariant submanifold is completely degenerate, i.e. if λ 2 = · · · = λ g = 0, then the submanifold must be an arithmetic Teichmüller curve in the moduli space of Abelian differentials over surfaces of genus three, four, or five. As a corollary, we prove that there is at most a finite number of such Teichmüller curves.
IntroductionThe Lyapunov exponents of the Kontsevich-Zorich (KZ) cocycle give information about the dynamics of numerous systems such as billiards in polygons with rational angles, interval exchange transformations and the Teichmüller geodesic flow on the moduli space of Abelian differentials on Riemann surfaces. More precisely, we consider the Lyapunov exponents of the KZ-cocycle on the absolute cohomology bundle over affine SL 2 (R)-invariant submanifolds of the moduli space of Abelian differentials on genus g surfaces. These exponents were studied extensively in [For02], [AV07] and [EKZ14]. In [For02], it was proved that the smallest non-negative exponent is always positive with respect to the canonical measures on strata of the moduli space of Abelian differentials. In [AV07], the KZ conjecture was verified using techniques independent of [For02], i.e. when the spectrum of 2g exponents of the cocycle is simple with respect to the canonical measures on strata. Explicit formulae for sums of the positive Lyapunov exponents of the KZ-cocycle were given in [EKZ14]. On the contrary, there are examples of orbit closures where the Lyapunov exponents are zero. An affine invariant submanifold with λ 2 = · · · = λ g = 0 is said to have completely degenerate KZ-spectrum. In this paper, we prove the following theorem.