Regulators and Heights in Algebraic Geometry

The Mahler measure of curves and surfaces
by Marie José Bertin Université Pierre et Marie Curie (Paris 6), Institut de Mathématiques de Jussieu

I report on some new examples of explicit logarithmic Mahler measures of multivariate polynomials.
When the polynomial defines a parametrizable curve, its Mahler measure is expressed in terms of Bloch-Wigner dilogarithms of an element of the Bloch group of an imaginary quadratic field ( Thus a link with hyperbolic varieties). When the polynomial defines a singular K3-surface, I give several examples of the Mahler measure expressed in terms of the L-series of the K3-surface for s=3. Dedekind zeta motives for totally real fields by Francis Brown CNRS, Institut de Mathématiques de Jussieu, IHES

On singular Bott-Chern classes
by José Ignacio Burgos Gil Universidad de Barcelona

The singular Bott-Chern classes measure the failure of an exact Riemann-Roch theorem for closed immersions at the level of currents. They are the key ingredient in the definition of direct images of hermitian vector bundles under closed immersions and in the proof of the arithmetic Riemann-Roch theorem in Arakelov geometry for closed immersions. There are two definitions of singular Bott-Chern classes. The first due to Bismut, Gillet and Soulé uses the formalism of super connections. The second, due to Zha, is an adaptation of the original definition of Bott-Chern classes by Bott and Chern.In this talk we will give an axiomatic characterization of singular Bott-Chern classes, which is similar to the characterization of Bott-Chern forms, but that depends on the choice of an arbitrary characteristic class. This characterization allow us to give a new definition of singular Bott-Chern forms by means of the deformation to the normal cone technique and to compare the previous definitions of singular Bott-Chern forms. Moreover we will give an explicit computation of the characteristic class associated to Bismut-Gillet-Soulé definition of singular Bott Chern currents.

Generic p-rank of semi-stable fibration
by Junmyeong Jang Purdue University

In this presentation, I will be concerned with two pathological phenomenons of positive characteristic, the failure of Miyaoka-yau inequality and the failure of semi-positivity theorem. Szpiro showed that a Frobenius base change of non-isotrivial smooth fibration violates Miyaoka-Yau inequality. For such a fibration, if the p-rank of the generic fiber is maximal, the dimension of the Lie algebra of Picard scheme is stable after the Frobenius base change. Using this fact and a reduction argument we can construct a counter example of Miyaoka-Yau inequality with smooth Picard scheme, which is a counterexample of Parshin's expectation. And we will see for a semi-stable fibration p : X ? C of a proper smooth surface to a proper smooth curve, if the p-rank of the generic fiber is maximal, the semi-positivity theorem holds and if the p-rank of the generic fiber is 0, some Frobenius base change of p violates the semi-positivity theorem. This result may be applied to a problem of the distribution of p-ranks of reductions of a certain non-closed point in the moduli space of curves over Q¯.

The Abel-Jacobi map on the Einsestein symbol
by Matthew Kerr Durham University

In this talk we consider two different constructions of motivic cohomology classes on families of toric hypersurfaces and on Kuga varieties. Under certain modularity conditions on the former we say how the constructions "coincide", obtaining a complete explanation of the phenomenon observed by Villegas, Stienstra, and Bertin in the context of Mahler measure. (This is where the AJ computation on the Kuga varieties, done using our formula with J. Lewis and S. Mueller-Stach, will be summarized). We also look at an application of the toric construction in the non-modular case, to limits of normal functions for families of Calabi-Yau 3-folds.

Moduli of polarized logarithmic Hodge structures and period maps
by Sampei Usui Osaka University

Height and GIT weight
by Xiaowei Wang The Chinese University of Hong Kong

In this talk, we will establish a new connection between the weight in the geometric invariant theory and the height introduced by Cornalba and Harris CH and Zhang Z. Then I will explains two applications of this connection.

Talks will be held at CAB 269 (April 12, 14, 15, 16) and ETL E1 008 (April 13). We have booked the computer lab at CAB 341. map