Genus Two Meromorphic Conformal Field Theory

We construct the genus two (or two loop) partition function for meromorphic bosonic conformal field theories. We use a sewing procedure involving two genus one tori by exploiting an explicit relationship between the genus two period matrix and pinching modular parameters. We obtain expressions for the partition function for the chiral bosonic string, even rank lattice theories and self-dual meromorphic conformal field theories including the Moonshine Module. In particular, we find that for self-dual theories with central charge 24, the genus two partition function multiplied by a universal holomorphic function of the moduli is given by a meromorphic Siegel modular form of weight 2 where this universal function includes ghost contributions. We also discuss a novel expansion for certain Siegel modular forms.Comment: 25 pages, AMS Latex2e, 2 figures, Talk presented at Workshop on Moonshine, CRM, Montreal, May 29 to June 4, 199

The geometry of maximal representations of surface groups into SO(2,n)

In this paper, we study the geometric and dynamical properties of maximal representations of surface groups into Hermitian Lie groups of rank 2. Combining tools from Higgs bundle theory, the theory of Anosov representations, and pseudo-Riemannian geometry, we obtain various results of interest. We prove that these representations are holonomies of certain geometric structures, recovering results of Guichard and Wienhard. We also prove that their length spectrum is uniformly bigger than that of a suitably chosen Fuchsian representation, extending a previous work of the second author. Finally, we show that these representations preserve a unique minimal surface in the symmetric space, extending a theorem of Labourie for Hitchin representations in rank 2.Comment: 56 pgs, section 3 has been reorganized , former sections 4.2 and 4.3 have been merged into section 4.2 and rewritten to avoid reference to maximal surfaces and Higgs bundles, appendix added on strong version of Ahlfors-Schwarz-Pick lemma. To appear in Duke Math Journa

Higher Teichm\"uller Spaces: from SL(2,R) to other Lie groups

The first part of this paper surveys several characterizations of Teichm\"uller space as a subset of the space of representation of the fundamental group of a surface into PSL(2,R). Special emphasis is put on (bounded) cohomological invariants which generalize when PSL(2,R) is replaced by a Lie group of Hermitian type. The second part discusses underlying structures of the two families of higher Teichm\"uller spaces, namely the space of maximal representations for Lie groups of Hermitian type and the space of Hitchin representations or positive representations for split real simple Lie groups.Comment: The file uploaded on May 12th was the wrong one and did not contain the Section 4.6 that was added. This is the version to appear in the Handbook of Teichm\"uller theor

Genus 0, 1, 2 actions of some almost simple groups of lie rank 2

Please see the paper. Thanks