Perverse sheaves on semiabelian varieties

We give a Tannakian description for categories of l-adic perverse sheaves on semiabelian varieties which combines a construction of Gabber and Loeser for algebraic tori with a generic vanishing theorem for the cohomology of constructible sheaves on abelian varieties. As an application we explain how the arising Tannaka groups on abelian varieties can be studied in terms of semiabelian degenerations via the functor of nearby cycles.Comment: 14 page

Summands of theta divisors on Jacobians

We show that the only summands of theta divisors on Jacobians of curves and on intermediate Jacobians of cubic threefolds are the obvious powers of the curve and the Fano surface of lines on the threefold. The proof uses the decomposition theorem for perverse sheaves, a bit of representation theory and a computation of characteristic cycles for Brill-Noether sheaves.Comment: references updated, background on fiber functors and lambda rings added, proof of 2.5 made self-containe

Vanishing Theorems for constructible Sheaves on Abelian Varieties

We show that the hypercohomology of most character twists of perverse sheaves on a complex abelian variety vanishes in all non-zero degrees. As a consequence we obtain a vanishing theorem for constructible sheaves and a relative vanishing theorem for a homomorphism between abelian varieties. Our proof relies on a Tannakian description for convolution products of perverse sheaves, and with future applications in mind we discuss the basic properties of the arising Tannaka groups

Constraints on models with universal extra dimensions from dilepton searches at the LHC

Models with universal extra dimensions predict that each Standard Model particle is accompanied by a tower of Kaluza-Klein resonances. Canonical searches for the production and cascade decays of first Kaluza-Klein modes through missing transverse momentum signatures suffer in general from low detection efficiencies because of the rather compressed Kaluza-Klein particle mass spectrum. Here, instead we analyze signatures from the production of second Kaluza-Klein states which can decay into Standard Model particles and thus do not result in any missing transverse momentum. Such signatures provide a strong sensitivity, and are of particular interest as they would allow for a clear distinction between extra dimension models and other models of new physics like supersymmetry. We constrain the production of second Kaluza-Klein particles from recent LHC searches for dilepton resonances, and place limits on the compactification scale to be larger than 715GeV, and on the masses of the second Kaluza-Klein particles to be larger than 1.4TeV.Comment: 11 pages, 4 figures, analysis updated (inclusion of data from CMS-PAS-EXO-12-061), MUED bound improved to R^{-1} > 715 GeV, version published in JHE