Metrics with cone singularities along normal crossing divisors and holomorphic tensor fields

We prove the existence of non-positively curved K\"ahler-Einstein metrics with cone singularities along a given simple normal crossing divisor on a compact K\"ahler manifold, under a technical condition on the cone angles, and we also discuss the case of positively-curved K\"ahler-Einstein metrics with cone singularities. As an application we extend to this setting classical results of Lichnerowicz and Kobayashi on the parallelism and vanishing of appropriate holomorphic tensor fields.Comment: 36 pages, v3: added a section on the log-Fano case. To appear in Annales Scientifiques de l'EN

EL-Shellability and Noncrossing Partitions Associated with Well-Generated Complex Reflection Groups

In this article we prove that the lattice of noncrossing partitions is EL-shellable when associated with the well-generated complex reflection group of type $G(d,d,n)$, for $d,n\geq 3$, or with the exceptional well-generated complex reflection groups which are no real reflection groups. This result was previously established for the real reflection groups and it can be extended to the well-generated complex reflection group of type $G(d,1,n)$, for $d,n\geq 3$, as well as to three exceptional groups, namely $G_{25},G_{26}$ and $G_{32}$, using a braid group argument. We thus conclude that the lattice of noncrossing partitions of any well-generated complex reflection group is EL-shellable. Using this result and a construction by Armstrong and Thomas, we conclude further that the poset of $m$-divisible noncrossing partitions is EL-shellable for every well-generated complex reflection group. Finally, we derive results on the M\"obius function of these posets previously conjectured by Armstrong, Krattenthaler and Tomie.Comment: 37 pages, 4 figures. Moved the technical details of the proof of the EL-shellability of $NC_{G(d,d,n)}$ to the appendix. More references adde

Construction of Hamiltonian-minimal Lagrangian submanifolds in complex Euclidean space

We describe several families of Lagrangian submanifolds in the complex Euclidean space which are H-minimal, i.e. critical points of the volume functional restricted to Hamiltonian variations. We make use of various constructions involving planar, spherical and hyperbolic curves, as well as Legendrian submanifolds of the odd-dimensional unit sphere.Comment: 23 pages, 5 figures, Second version. Changes in statement and proof of Corollary

Connectivity Properties of Factorization Posets in Generated Groups

We consider three notions of connectivity and their interactions in partially ordered sets coming from reduced factorizations of an element in a generated group. While one form of connectivity essentially reflects the connectivity of the poset diagram, the other two are a bit more involved: Hurwitz-connectivity has its origins in algebraic geometry, and shellability in topology. We propose a framework to study these connectivity properties in a uniform way. Our main tool is a certain linear order of the generators that is compatible with the chosen element.Comment: 35 pages, 17 figures. Comments are very welcome. Final versio