On the Newton polygons of abelian varieties of Mumford's type

Let $A$ be an abelian variety of Mumford's type. This paper determines all possible Newton polygons of $A$ in char $p$. This work generalizes a result of R. Noot.Comment: 15 page

Complex multiplication, Griffiths-Yukawa couplings, and rigidity for families of hypersurfaces

Let M(d,n) be the moduli stack of hypersurfaces of degree d > n in the complex projective n-space, and let M(d,n;1) be the sub-stack, parameterizing hypersurfaces obtained as a d fold cyclic covering of the projective n-1 space, ramified over a hypersurface of degree d. Iterating this construction, one obtains M(d,n;r). We show that M(d,n;1) is rigid in M(d,n), although the Griffiths-Yukawa coupling degenerates for dn the sub-stack M(d,n;2) deforms. We calculate the exact length of the Griffiths-Yukawa coupling over M(d,n;r), and we construct a 4-dimensional family of quintic hypersurfaces, and a dense set of points in the base, where the fibres have complex multiplication.Comment: 38 pages, amsLaTeX, second version: Correction of a wrong statment in Section 8; References updated, some typos corrected (including one in the title

On the slope conjecture of Barja and Stoppino for fibred surfaces

Let $f:\,S \to B$ be a locally non-trivial relatively minimal fibration of genus $g\geq 2$ with relative irregularity $q_f$. It was conjectured by Barja and Stoppino that the slope $\lambda_f\geq \frac{4(g-1)}{g-q_f}$. We prove the conjecture when $q_f$ is small with respect to $g$; we also construct counterexamples when $g$ is odd and $q_f=(g+1)/2$.Comment: any comment is welcom

A characterization of certain Shimura curves in the moduli stack of abelian varieties

Let f:X-->Y be a semi-stable family of complex abelian varieties over a curve Y of genus q, and smooth over the complement of s points. If F(1,0) denotes the non-flat (1,0) part of the corresponding variation of Hodge structures, the Arakelov inequalities say that 2deg(F(1,0)) is bounded from above by g=rank(F(1,0))(2q-2+s). We show that for s>0 families reaching this bound are isogenous to the g-fold product of a modular family of elliptic curves, and a constant abelian variety. For s=0, if the flat part of the VHS is defined over the rational numbers, the family is isogeneous to the g-fold product of a family h:Z-->Y, and a constant abelian variety. In this case, h:Z-->Y is obtained from the corestriction of a quaternion algebra A, defined over a totally real numberfield F, and ramified over all infinite places but one. In case the flat part of the VHS is not defined over the rational numbers, we determine the structure of the VHS.Comment: 42 pages, AMSLaTeX, Added one proposition, one remark, and erased one chapter with examples. References update

Weierstrass filtration on Teichmuller curves and Lyapunov exponents

We define the Weierstrass filtration for Teichmuller curves and construct the Harder-Narasimhan filtration of the Hodge bundle of a Teichmuller curve in hyperelliptic loci and low-genus nonvarying strata. As a result we obtain the sum of Lyapunov exponents of Teichmuller curves in these strata.Comment: 28 pages. Published version in Journal of Modern Dynamics. arXiv admin note: text overlap with arXiv:1104.3932 by other author

Complex projective threefolds with non-negative canonical Euler-Poincare characteristic

Let $V$ be a complex nonsingular projective 3-fold of general type with $\chi(\omega_V)\geq 0$ (resp. $>0$). We prove that the m-canonical map $\Phi_{|mK_V|}$ is birational onto its image for all $m\ge 14$ (resp. $\geq 8$). Known examples show that the lower bound $r_3=14$ (resp. $=8$) is optimal.Comment: 20 pages, to appear in "Communications in Analysis and Geometry

Weierstrass filtration on Teichm\"uller curves and Lyapunov exponents: Upper bounds

We get an upper bound of the slope of each graded quotient for the Harder-Narasimhan filtration of the Hodge bundle of a Teichm\"{u}ller curve. As an application, we show that the sum of Lyapunov exponents of a Teichm\"{u}ller curve does not exceed ${(g+1)}/{2}$, with equality reached if and only if the curve lies in the hyperelliptic locus induced from $\mathcal{Q}(2k_1,...,2k_n,-1^{2g+2})$ or it is a special Teichm\"{u}ller curve in $\Omega\mathcal{M}_g(1^{2g-2})$. It also gives an unified interpretation for many known results about the special partial sums of Lyapunov exponents on Teichm\"uller curves.Comment: 19 page. We rewrite this paper without changing the mathematics conten

On Shimura curves in the Torelli locus of curves

Oort has conjectured that there do not exist Shimura curves lying generically in the Torelli locus of curves of genus $g \geq 8$. We show that there do not exist one-dimensional Shimura families of semi-stable curves of genus $g\geq 5$ of Mumford type. We also show that there do not exist Shimura curves lying generically in the Torelli locus of hyperelliptic curves of genus $g\geq 8$. The first result proves a slightly weaker form of the conjecture for the case of Shimura curves of Mumford type. The second result proves the conjecture for the Torelli locus of hyperelliptic curves. We also present examples of Shimura curves contained generically in the Torelli locus of curves of genus $3$ and $4$.Comment: 42 pages. Some typos are corrected. comments are welcom

Discreteness of minimal models of Kodaira dimension zero and subvarieties of moduli stacks

We extend some of the results obtained for subvarieties of the moduli stack of canonically polarized manifolds in "Base spaces of non-isotrivial families of smooth minimal models" (math.AG/0103122) to moduli of polarized minimal models of Kodaira dimension zero. To this aim we first show that for those manifolds there are no non isotrivial families of minimal models, which are birationally isotrivial. In the last chapter, we discuss the rigidity of curves in the moduli stack of canonically polarized manifolds and of polarized minimal models of Kodaira dimension zero.Comment: 26 pages, AMSLaTeX, 3nd version with some minor corrections and a new introductio

Families of abelian varieties over curves with maximal Higgs field

Let f:X-->Y be a semi-stable family of complex abelian varieties over a curve Y of genus q, and smooth over the complement of s points. If F(1,0) denotes the non-flat (1,0) part of the corresponding variation of Hodge structures, the Arakelov inequalities say that 2deg(F(1,0)) is bounded from above by g=rank(F(1,0))(2q-2+s). We show that for s>0 families reaching this bound are isogenous to the g-fold product of a modular family of elliptic curves, and a constant abelian variety. The content of this note became part of the article "A characterization of certain Shimura curves in the moduly stack of abelian varieties" (math.AG/0207228), where we also handle the case s=0.Comment: 13 pages, Latex, two minor errors corrected, the content of this note became part of math.AG/020722